
Class JlX^m 
Book -L S I 
(xm^M" '. 



COFYRIGHT DEPOSrr. 



SELECT METHODS 



IN 



FOOD ANALYSIS 



BY 



HENRY LEFFMANN, A.M., M.D., PH.D. 



AND 



WILLIAM BEAM, A.M., M.D., F.I.G. 



SECOND EDITION, REVISED AND ENLARGED 



Mitb ®ne HMate anO 
54 ©tber IHluetratlons 



PHILADELPHIA 

P. BLAKISTON'S SON & CO. 

I0I2 WALNUT STREET 
1905 



LIBRARY of : 


ONGRESS 


Twu Copie!> 


iieu»«6'j 


JUN 8 


lyoi) 




//7^ J/ 

«JUKT B. 



V 



CorvRiGHT, 1905, 15Y P. Blakiston's Son & Co. 



PRESS OF 

WM. F. FELL COMPANY 

PHILAOCLPHI A 



PREFACE TO SECOND EDITION 



The rapid sale of the first edition of this work, and the favor- 
able opinions expressed in reviews and correspondence, have 
encouraged the authors to prepare a second edition, which it is 
hoped will be worthy of the position attained by the first. The 
preparation of the second edition has been considerably de- 
layed, and in the interval much progress has been made in the 
field. American work is rapidly becoming the leader in food- 
analysis. The excellent equipment of the laboratories of the 
Department of Agriculture at Washington, supplemented by 
more than two-score of State experiment stations, and by hun- 
dreds of investigators, connected with Boards of Health and 
Food Commissioners, enables every problem to be submitted to 
prompt and searching inquiry. We have endeavored to utilize 
this material fully. It is to be regretted that the publication 
of these investigations is still unsatisfactory, important results 
often appearing in bulletins of local circulation and limited 
editions. It is to be hoped that some system of international 
publication, easy of access, will be instituted. 

In the present edition much alteration has been made. Many 
paragraphs have been cancelled and much new matter inserted. 
Among the additions are: Detailed descriptions of special 
arrangements for polarimctry, distillation and extraction; new 
processes for detection of natural colors used as substitutes for 
fruit and egg-colors; improvements in detection of formaldehyde, 
abrastol and saccharin; rapid methods for examination of 
vanilla and lemon extracts, and for the determination of fat in 
condensed milk and cereal foods; determination of boric acid in 



111 



IV PRKFACF. TO THK SECOND KDITIOX 

fruit-juiccs; analytic data in regard to fruit-juices, jams and 
jellies; detection of palm oil in oleomargarin, and many minor 
modifications of tests and processes intended to simplify or ex- 
pedite analysis. 

The purpose of the book has not been modified. It is for the 
practical worker in the detection of food adulteration. No 
space has been given to discussion of the etTects of adulteration, 
nor to the principles to be observed in the establishment of 
food-standards, or in framing or administering food-laws. 
These are not matters for the analyst. The standards pub- 
lished Ijy the U. S. Government have been included as olTicial 
interpretations of analytic data. 

All temperatures are centigrade. Unless otherwise noted, 
all readings of scale or arc are positive; sulfuric, nitric and 
hydrochloric acids and ammonium hydroxid are the standard 
concentrated pure grades of these reagents; alcohol is 95 per 
cent. 

Philadelphia, ^fay, 1905. 



ADDITIONS AND CORRECTIONS 

Page 64, after line 3, insert " For special methods for detection and determin- 
ation of aluminum, see pages 378 and 386." 

Page 79, after line 4, insert "Aluminum oxyacetate is sometimes used as a 
meat-preservative; see pages 378 and 386." 

Page 139, line 3, insert after " Iliibr' the reference-figure ''. 

Pa^e 140, line 16 from bottom, for *^ read '\ 

Page 349, line 13, for *' lo per cent," read " 16 per cent." 



NOTE SPECIAL PAGE FOLLOWING INDEX 



CONTENTS 



ANALYTIC METHODS 
Physical Data: page 
Specific Gravity — Melting and Solidifying Points — Boiling- 
point — Polarimetry — Spectroscopy — Fluorescence — Micros- 
copy, 1-26 

Chemical Data: 

Water and Fixed Solids (Extract) — Nitrogen — Crude Fiber — 
Ash — Extraction with Miscible Solvents — Extraction with Im- 
miscible Solvents — Distillation and Sublimation — Apparatus 
and Chemicals, 27-56 

APPLIED ANALYSIS 
General Methods: 

Poisonous Metals — Colors — -Preservatives, 57~S6 

Special Methods: 

Starch, Flours, and Meals — Bread — Leavening Materials — 

Sugars — Honey — Candies and Confections, 86-136 

Fats and Oils: lodin Number — Volatile Acids — Saponification 
Value — Acid Value — Solubility in Acetic Acid — Thermal Reac- 
tion with Sulfuric Acid — Specific Temperature Reaction — 
Bromin Thermal Value — Elaidin Test — Refractive Index — 
Soluble and Insoluble Acids — Cholesterol and Analogs — 
Acetyl Value — Unsaponifiable Matter — Analytic Data — Special 

Tests, 137-168 

Olive Oil — Cottonseed Oil — Maize Oil — Arachis Oil — -Sesame 
Oil — Rape Oil — Coconut Oil — Cacao-butter — Lard — Butter- 
fat, 168-1S9 

Milk and Milk Products: Milk — Condensed Milk — Butter — • 

Cheese — Fermented Milk Products, 190-251 

Non-alcoholic Beverages: Tea — Coffee — Cacao, 251-2S2 

Condiments and Spices: Vinegar — Pepper — Long Pepper — 
Cayenne Pepper — Ginger — Nutmeg — Mace — Allspice — Cinna- 
mon — Cloves — Mustard — Flavoring Extracts — Fruit-products 
Table Accessories and Desserts — Egg-substitutes, 282-336 

V 



vi CONTEXTS 

Special Methods {Cotitinu^d): pace 
,1 koholic Beverat^cs: Cider — Spirits — Whiskey — Brandy — Gin 
—Rum — Malt Li(|Uors — Wine — Alcohol Tables — Malt Ex- 
tracts, 337-372 

Flesh Foods: Meats — Meat-extracts, 373-3^5 



Appendix. Tables — References, 386-388 

Index. 



FOOD ANALYSIS 



ANALYTIC METHODS 

PHYSICAL DATA 

Specific Gravity. 

In food analysis, determination of specific gravity of solids is 
rarely made. Fats are usually tested in the melted condition. 

The following method for solid fats, due to Hager, is suita- 
ble for small amounts of material: The sample is melted and 
allowed to drop slowly from the height of about 3 centimeters 
into some cold alcohol in a dish. The globules thus obtained 
are placed in diluted alcohol at 15.5°, the strength of which 
is so adjusted that the globules float in any part of the liquid. 
The specific gravity of the liquid is then determined; it is, of 
course, the same as that of the globules. Many substances 
when cooled suddenly are liable to have abnormal density, 
hence it is preferable, as noted by Allen, to use fragments 
cut from a solid mass cooled under normal conditions and 
allowed to stand at least twenty-four hours. 

The specific gravity of a liquid is generally expressed by 
comparison with water. Confusion and inconvenience have 
arisen from the fact that results have been referred to water at 
different temperatures as unity. It is becoming customary 
to express, as is proper, the temperatures of observation and 
comparison. ^°°o indicates a determination at 100° and com- 



2 FOOD ANALYSIS 

parison with water at 15.5° as unity. It is best to compare 
the substance and the standard at the same temperature. 

Pyknometer or Sped fie -gravity Bottle. — This is an accurate, 
generally applicable means of determining specific gravity. It 
is a bottle with a perforated stopper, adjusted to hold a 
certain weight of water at a standard temperature, usually 
15.5°. Bottles as sold are often inaccurate. The weight of 
water that a bottle holds should be carefully determined. 

E. R. Squibb devised a convenient form of pyknometer (fig- 
ure i) which permits the determination to be made at any 
temperature between o and 25°, and compared 
with water at the same temperature. The bottle 
should hold 100 grams of recently-boiled distilled 
water at 20° at about 58 on a scale of o to 100. 
In weighing the water into the bottle, the fine adjust- 
ment to o.ooi gram is made by use of narrow strips 
of blotting-paper that will pass easily down the bore 
of the graduated stem. When the 100 grams are in 
the bottle, and the column stands between 50 and 
65 divisions of the scale, the stopper is put in, a 
leaden ring is put on the neck, and the whole im- 
j7jQ J mersed in a bath of broken ice and water until 
the column of water comes to rest. It should then 
read at zero of the scale, or not much above it, and the read- 
ing should be noted. If it reads below zero, the bottle is too 
large, and the stopper part of the stem must be ground farther 
into the bottle neck, until the reading, on new trial, brings the 
column a little above zero. The bottle is then put into a bath 
at 25° and kept there, with stirring of the bath, until the 
column comes to rest, when it should read somewhere from 
90 to TOO of the scale. Should it read above 100, while the 
lower limit is as far above the zero, the bottle is too small, and 
the end of the stopper must be ground off until the reading of 
the column is within the graduations at both ends of the scale. 




SPECIFIC GRAVITY 3 

Sprengel Tube. — This is a form of pyknometer with which 
a high degree of accuracy is attainable. It is especially suita- 
ble for determinations at the boiling-point of water. It con- 
sists (figure 2) essentially of a thin glass U-tube terminating 
in two capillary ends bent at right angles and each provided 
with a ground cap. • One of these capillary tubes must have 
a smaller caliber than the other — not larger than 0.25 mm. 
The larger tube should bear a mark at m. The tube is filled 
by immersing h in the liquid under examination, connecting 





Fig. 2. 



Fig. 3. 



the smaller end with a large glass bulb, and applying suction 
to the latter by means of a rubber tube, as shown in figure 3. 
If now the rubber tube be closed, the glass tube will fill auto- 
matically. It is placed in water, the ends being allowed to 
project, and the water is brought to the proper temperature. 
A conical flask may be used to contain the water, the ends 
of the Sprengel tube being supported by the neck. The 
mouth of the flask should be loosely covered. As the liquid 



4 FOOD ANALYSIS 

expands it will drop from the larger orifice. When this ceases, 
the hquid is adjusted to the mark at ;;/. If beyond the point, 
a Httle may be extracted by means of a roll of paper. The 
tube is then taken out of the bath, the caps adjusted, the 
whole thoroughly dried, allowed to cool, and weighed. The 
same operation having been performed with distilled water, 
the calculation of the specific gravity is made as usual. 

Westphal Balance. — This affords a convenient means of 
determining specific gravity. It consists of a delicate steel- 




FlG. 4. 



yard provided with a counterpoised plummet. The latter, 
being immersed in the liquid, the equilibrium is restored by 
means of weights or riders, the value of which is directly ex- 
pressed in figures for the specific gravity without calculation. 
Thus, the rider A' is of such a weight as to express the first 
decimal place, and will be represented by any of the figures 
from o to 9 according to its position on the beam. Similarly 
the riders A, B and C furnish the figures for the second, third 
and fourth decimal places respectively. The weight A" is 
used in the case of liquids heavier than water. 



SPECIFIC GRAVITY 5 

The ordinary form of Westphal balance is untrustworthy, 
but good instruments are made by some European manu- 
facturers. 

The principle of the hydrostatic balance may be applied 
by using a plummet (that sold with the Westphal balance 
will serve) with the ordinary analytic balance. Test-tubes 
weighted with mercury and sealed in the flame may also be 
used. The plummet is suspended to the hook of the balance 





Fig. 5. 



Fig. 6. 



by means of a fine platinum wire. The specific gravity of any 
liquid may be determined by noting the loss of weight of the 
plummet when immersed in the liquid and dividing this by 
the loss in pure water. 

If the determination be made at the boiling-point of water, 
the arrangements shown in Figs. 5 and 6 may be employed. 
The temperature of the liquid will not usually rise above 99°. 
This may be done with a hydrometer or balance, if the cylin- 



6 FOOD ANALYSIS 

der containing the oil be kept for a sufficient time in boiling 
water. With the Sprengel tube high accuracy may be ob- 
tained. The weight of the Sprengel tube and that of water 
contained at 15.5° being known, the tube should be com- 
pletely filled with the oil, by immersing one of the orifices in 
the liquid and sucking at the other. The tube is placed in a 
conical flask containing water which is kept actively boiling, a 
porcelain crucible-cover being placed over the mouth of the 
flask. The oil expands and drops from the orifices. When 
this ceases, the oil adhering to the outside is removed by the 
cautious use of filter-paper, the tube removed, wiped dry, 
cooled, and weighed. The weight of the contents divided by 
the w^eight of water contained at 15.5° will give the specific 
gravity at the temperature attained compared with water at 
i5-5°- When the amount of material is sufficient, the deter- 
mination may be made by use of the plummet, employing a 
cylindrical bath with two orifices. One of these is fitted with 
an upright tube for conveying the steam away from the neigh- 
borhood of the balance; into the other a test-tube, 15 cm. in 
length and 2.5 cm. in diameter, fits tightly, the joint being 
made perfect by cork or india-rubber. The test-tube is filled 
with the substance to be tested, and the plummet immersed 
in it. The water in the outer vessel is then kept in constant 
ebullition, until a thermometer, with which the oil is repeat- 
edly stirred, indicates a constant temperature, when the plum- 
met is attached to the lever of the balance, and counterpoised. 
For temperatures higher than 100° glycerol or paraffin may 
be used, but considerable care is required in such cases. 

Hydrometers are much used for the determination of the 
specific gravity of liquids, but the indications are less reliable 
than by the methods described above. The instruments as 
furnished are often not accurately graduated, and the zero 
point, at least, should be verified by immersing in distilled 
water at a standard temperature. Sensitive hydrometers with 



MELTING AND SOLIDIFYING POINTS 7 

slender stems, accurately graduated, are now obtainable. 
These are capable of furnishing good results. Care should 
be taken to make the reading at the top, center or bottom 
of the meniscus according to the method used in the grad- 
uation of the instrument. Instruments intended for use with 
opaque liquids should be graduated to be read at the top of 
the meniscus. 

The actual specific gravity of any substance is the ratio of 
its density at a given temperature to that of water at the same 
temperature. Statements made upon any other basis than this 
may be converted into actual specific gravity by calculation 
from the table of density of water given in the appendix. 

too" 

Thus, a determination of specific gravity of 0.8000 at ^ 
may be converted into actual specific gravity (^) as follows: 

Density of water at 15° =0.99916. 
100° = 0.95866. 

TOO° 100° 

15° 100° 

Therefore, 95866 : 99916 : : 0.8000 : 0.8337 (actual specific gravity at 100°). 

Melting and Solidifying Points. 

The determination of these is often difficult. Many sub- 
stances, especially fats, assume conditions exhibiting abnormal 
melting-points, and also frequently solidify at a temperature 
very different from that at which they melt. If, in the prep- 
aration of any substance for determining its melting-point, it 
is necessary to make a previous fusion, the mass should be 
allowed to rest not less than twenty-four hours after solidifi- 
cation before making the experiment. Chemists disagree as to 
whether the melting-point should be considered to be that at 
which the substance begins to be liquid or that at which the 
liquid is perfectly clear. Ordinary thermometers are frequently 
inaccurate, the error amounting to a degree or more. No ob- 
servations in which precision is required should be made with 
unverified instruments. 



8 



FOOD ANALYSIS 



The following method for determining melting-points is 
suitable for many technical purposes. By substituting strong 
brine or glycerol for the water in the bath observations may 
be made at temperatures beyond the limits of o° and ioo°: 

The substance is heated to a temperature slightly above its 





c. 




Fig. 7. 



Fig. 8. 



fusing-point, drawn into a very narrow glass tube, and allowed 
to solidify for not less than twenty- four hours. The tube, open 
at both ends, is attached by a wire or rubber ring to a thermom- 
eter so that the part containing the substance is close to the 
bulb. The apparatus, immersed in water, is heated at a rate 
not exceeding 0.5° per minute until fusion takes place, when 



MELTING AND SOLIDIFYING POINTS 9 

the temperature is noted. The temperature is allowed to fall 
and the point at which the substance becomes solid is also 
observed. To insure uniform and gradual heating, it is neces- 
sary to immerse the vessel containing the thermometer and 
tube in another larger vessel filled with water. Allen sug- 
gests a flask of which the neck has been cut off, as shown in 
figure 7. A neater form of apparatus is shown in figure 8, 
from "Richter's Organic Chemistry." 

The two following methods are especially adapted to the 
examination of fats and waxes. The A. O. A. C. method dis- 
regards the abnormal condition of recently-solidified masses: 

A. O. A. C. Method. — A mixture of alcohol and water of 
the same specific gravity as the sample is prepared in the fol- 
lowing manner: Separate portions of distilled water and 95 
per cent, alcohol are boiled for 10 minutes. The water is 
poured, while still hot, into the test-tube described below 
until it is nearly half full. The test-tube is nearly filled with 
the hot alcohol, which is carefully poured down the side of 
the inclined tube to avoid too much mixing. If the alcohol 
is added when water is cold, the mixture will contain air- 
bubbles and be unfit for use. 

The apparatus (Fig. 9) consists of: A thermometer reading 
easily and accurately to tenths of a degree; a cathetometer 
for reading the thermometer (this may be substituted by an 
eyeglass if held steadily and properly adjusted); a thermom- 
eter; a tall beaker 35 cm. high and 10 cm. in diameter; a 
test-tube 30 cm. long and 3.5 cm. in diameter; a stand for 
supporting the apparatus; some method of stirring the water 
in the beaker (for example, a rubber blowing-bulb and a glass 
tube extending to near the bottom of the beaker). 

The melted and filtered fat is allowed to fall from a drop- 
ping-tube from a height of from 15 to 20 cm. on a smooth 
piece of ice floating in recently-boiled distilled water. Disks 
from I to 1.5 cm. in diameter, and weighing about 200 mg., 



10 



FOOD ANALYSIS 



are formed. Pressing the ice under the water the disks float 
on the surface, and are easily removed with a steel spatula, 

The test-tube contain- 



cooled in the ice-water before using. 




Fig. 9. 



ing the alcohol and water is placed in a tall beaker containing 
water and ice, until cold. The disk of fat is then dropped 
into the tube from the spatula and at once sinks to the part 
of the tube where the density of the diluted alcohol is exactly 



MELTING AND SOLIDIFYING POINTS II 

equivalent to its own. The delicate thermometer is placed 
in the test-tube and lowered until the bulb is just above the 
disk. In order to secure an even temperature in all parts of 
the alcohol m^ixture in the vicinity of the disk, the thermom- 
eter is used as a stirrer. The disk having been placed in posi- 
tion, the water in the beaker is slowly heated and kept con- 
stantly stirred by means of the blowing apparatus already 
described. When the temperature of the alcohol-water mix- 
ture rises to about 6° below the melting-point, the disk of 
fat begins to shrivel and gradually rolls up into an irregular 
mass. The thermometer is lowered until the fat particle is 
even with the center of the bulb. The bulb of the thermom- 
eter should be small, so as to indicate only the temperature 
of the mixture near the fat. A gentle rotatory movement 
should be given to the thermometer bulb. The rise of tem- 
perature should be so regulated that the last 2° of increment 
require about ten minutes. The mass of fat gradually ap- 
proaches the form of a sphere, and when it is sensibly so the 
reading of the thermometer is taken. As soon as the tem- 
perature is taken the test-tube is removed from the bath and 
placed again in the cooler. A second tube, containing alcohol 
and water, is at once placed in the bath. The test-tube (ice- 
water having been used as a cooler) is of low enough tem- 
perature to cool the bath sufficiently. After the first deter- 
mination, which should be only a trial, the temperature of 
the bath should be so regulated as to reach a maximum of 
about 1.5° above the melting-point of the fat under examina- 
tion. If the edge of the disk touches the sides of the tube 
a new trial should be made. Second and third results should 
show a near agreement. 

TiTER-TEST. — To eliminate error in determining melting- 
points of intimate mixtures, such as commercial fats and waxes, 
the titer-test, proposed by Dalican, has been largely adopted. 

100 grams of the fat are saponified, the fatty acids separated 



12 



POOD ANALYSIS 



by addition of acid, freed from water, filtered into a porcelain 
dish, and allowed to solidify overnight under a desiccator. 
The mass is then carefully melted in an air-bath and sufficient 
poured into a test-tube i6 cm. long and 3.5 cm. in diameter 
to fill the tube a little more than half-full. The tube is then 
placed in a suitable flask, say of 2000 c.c. capacity, and a deli- 
cate thermometer, indicating one-fifth of a degree, inserted so 
that the bulb reaches the center of the mass. When a 
few crystals appear at the bottom of the tube, 
the mass is stirred by giving the thermometer 
a rotatory movement, first three times from 
right to left, then three times from left to right, 
and then continuously, by a quick circular move- 
ment of the thermometer, without allowing it to 
touch the side of the vessel, but taking care that 
all solidifying portions, as they form, are well 
stirred in. The liquid will gradually become 
cloudy throughout, and the thermometer must be 
observed carefully. At first the temperature will 
fall, but will soon rise suddenly a few tenths of a 
degree and reach a maximum at which it remains 
stationary for a short time before it falls again. 
This point is called the "titer" or solidifying point. 

Boiling-point. 

Fig. 10. For the determination of boiling-point the ap- 

paratus of Berthelot is convenient. Figure 10, 
from Traube's "Physico- Chemical Methods," shows the con- 
struction. The thermometer is inclosed in an outer tube, so 
that the portion of the scale to which the mercury rises is 
immersed in the vapor. If this be not done, a correction 
must be applied for the error produced by the cooling of the 
thermometer tube. The bulb of the thermometer does not 
reach into the liquid. A few fragments of pumice-stone or 




POLARIMETRY 1 3 

broken clay pipestems will prevent bumping. The exit-tube 
at the lower end of the wide tube connects with a condenser. 
The barometric pressure must always be noted and correction 
made for the variation from the standard pressure, 760 mm., 
by the following formula: 

B r= B^ + 0.0375 (760 — P); in which 
B is the boiHng-point at normal pressure, 
B^ the observed boihng-point, 
P the observed pressure in miHinieters. 

For an apparatus designed for special boiling-point observa- 
tions see under '' Alcoholic Beverages." 

Polarimetry. 

Polarimeters are instruments used to measure the extent 
and direction of the rotation of the plane of polarized light. 
They consist essentially of a Nicol's prism as polarizer, a tube 
carrying the substance to be tested, and a second Nicol's 
prism, or analyzer, by which the extent of rotation is meas- 
ured. In all forms some condition of the field of vision is 
fixed upon as the zero point, and the rotation of the analyzer 
or other manipulation necessary to restore this standard field 
affords the measurement of the rotation caused by tiie inter- 
posed substance. Several types of instrument have been de- 
vised, of which two are most important. In one form, de- 
vised by Soleil, white light is used and a colored field, known 
as the transition tint, is taken as the zero point. In the other 
type white light or monochromatic (yellow) light is used and 
the zero point determined by equalizing the brightness of the 
field. Instruments of the first form are unsatisfactory by 
reason of the difference in susceptibility in the eyes of differ- 
ent person to color-contrasts. The instruments of the second 
type, commonly designated shadow instruments (more cor- 
rectly, "penumbral"), are now more generally employed. 

In the Laurent apparatus, shown in figure 11, the mono- 



u 



FOOD ANALYSIS 



chromatic light passes through the coUimating lens A and is 
polarized by the Nicol's prism B, which is so placed that it may 
be moved, on its axis, over a small arc by means of the lever 
C and clamped at any point; by this the brightness of the 
field may be varied and the sensitiveness of the instrument in- 
creased or diminished as may be needed. The polarized beam 
then passes through a quartz plate of even thickness, cut ex- 
actly parallel to the optic axis, and placed so that it covers a 



s 

F E 




Fig. II. 



semicircle of the field. At the other end of the apparatus is 
the analyzing prism E and the eye-piece F fixed to a graduated 
disk. This combination can be rotated upon its axis in a com- 
plete circle. Attached arms csLvry view-lenses for reading the 
angle of rotation, and the instrument is set at zero by an in- 
dependent adjustment by which the analyzing prism is rotated 
without disturbing the position of the graduated disk. Ver- 
niers are provided for close measurement. The monochro- 



POLARIMETRY 1 5 

matic light must be obtained from a sodium flame, since the 
thickness of the quartz plate is adjusted to these rays. 

In use, the tube is filled with water, the instrument directed 
to the source of light, and the adjusting milled head turned 
until the disk is set at zero. The two portions of the field 
should now appear equally illuminated. If this is not the case, 
the position of the analyzer must be altered by means of the 
independent adjustment, the index remaining undisturbed at 
the zero point. 

The tube is filled with the liquid to be tested and again 
placed in the instrument. If optically active, the plane of the 
polarized light will be rotated and one-half of the field of 
observation will appear darker. The extent of rotation, which 
will depend upon the nature of the substance and its amount, 
is measured by rotating the analyzer to the right or left, as 
the case may be, until the halves of the field become equally 
illuminated. 

This instrument can be employed to measure the rotatory 
power of all classes of substances, but other forms give ac- 
curate indications only with substances which have the same 
dispersive power as quartz, unless monochromatic light be 
used. In the Schmidt and Hansch penumbral instrument, 
the division of the field is obtained by a special construction 
of the polarizing prism and the restoration is accomplished by 
the adjustment of compensating quartz- wedges constructed so 
as to produce in the zero position no rotation. When an 
optically active substance is interposed in the path of the ray, 
one of the quartz-wedges must be moved to an extent suffi- 
cient to overcome this rotation in order to retore the stan- 
dard field. The effect is dependent upon the fact that by this 
movement the thickness of the quartz is increased or dimin- 
ished until it compensates for the rotation produced by the 
solution. The extent of movement of the quartz is registered 
upon a linear gcalc, which is read by means of a lens and ver- 



i6 



FOOD ANALYSIS 



nicr. White light is employed in making the observations. 
A form of the Laurent instrument, with quartz- wedge com- 
pensation, and employing white light, is made. An instru- 
ment has been devised in which the field is divided vertically 
into three zones, the central one being a broad band. Dupll- 




FlG. 12. 



cate Nicol prisms are so arranged that the lateral zones agree 
in tint, thus making stronger contrast with the central zone. 
The jjolarimeter shown in figure 12 is now the standard 
instrument. It has been improved lately by the substitution 
of a heavy iron stand for the rickety tripod, but is still in- 
complete. It has two serious defects. The illumination of 



POLARIMETRY 1 7 

the scale is awkward, and it is not convenient for examina- 
tions at temperatures above normal. 

The illumination of the scale is done by a mirror over the 
eye-lens which receives light from the main lamp. This in- 
terferes with the eye reaching its highest sensitiveness. In 
the laboratory of one of us (L) the following arrangement 
has been adopted. The polarimeter is in the balance-room, 
close to a small opening in the board partition, on the other 
side of which is the source of light. In daylight work the 
scale can be read without special light, but if greater sensitive- 
ness of the eye is needed a focussing cloth is thrown over the 
instrument and operator, and the scale is illuminated by a 
small incandescent lamp. 



11 



operated by two dry cells. 
The lamp is inserted just 
under the mirror that re- 
flects the scale and is con- 
trolled by a make-circuit 
key as usual. 

For examinations at tem- 
peratures above normal, 
Leach employs a double Fig. 13. 

metal tube, similar to the 

ordinary condenser, the inner channel being heavily gilded to 
prevent corrosion by acid liquids. Arrangements must be made 
for taking temperatures during observation and for expansion 
and contraction of the liquid in the inner tube when this is 
closed by the glass fronts. For taking temperature, it is usual to 
provide a tube at the center, connecting with the annulus, in 
which a thermometer is inserted. For expansion, Cochran pro- 
vides a short tube at one end, communicating with the inner tube. 
Figure 13 is a sketch of a form designed by one of us (L) in 
which the expansion and temperature tubes are combined. It 
is made of brass. The inner tube is 197 mm. long. This 



1 8 FOOD ANALYSIS 

allows the standard length of 200 mm. to be obtained by 
washers, against which the glass circles rest. These are held 
in place by caps, which screw into the solid end-pieces. The 
inner tube and the surface on which the washers rest should 
be well gilded. The joints need not be brazed as the tem- 
perature will never be near that of the melting-point of soft 
solder. At each end, somewhat above the middle horizontal 
line and communicating with the annulus, is a short tube about 
0.7 cm. in diameter. These are for attachment of rubber 
tubes carrying water. By placing them above the middle 
line, the tube will lie properly in the trough of the instrument. 
In the middle is a tube 3 cm. high, of the same diameter as 
the inner tube and communicating with it. It must be in 
such direction as to be upright when the tube is in position 
in the instrument. This tube is for expansion and holds the 
thermometer, which is set down as far as possible without 
interfering with the observation. The thermometer should be 
about 20 cm. long, with a scale from 0° to 100°. It is easily 
fastened by slipping a short piece of rubber tube over it, and 
over the brass tube. Holes can be cut in a focussing cloth 
so that the instrument and operator can be in darkness, the 
scale being read by means of the electric lamp as noted above. 

A metal vessel holding several hters is provided with heating 
arrangements, a rubber tube leads from it to one of the water- 
tubes, and an exit is provided through the other. The water 
in the vessel is allowed to flow through the observation tube 
at such a rate as will maintain the proper temperature in it. 

As many of these examinations are for differential temper- 
ature readings, it will often be unnecessary to connect up the 
hot-water apparatus. The observation tube should be closed 
with corks, the annulus filled with hot water, all its openings 
similarly closed, and then placed in w^ater at a suitable tempera- 
ture for at least five minutes. It is removed, wiped dry, the 
glass fronts fastened in the usual way, and the liquid to be 



POLARIMETRY IQ 

examined run in through the thermometer opening. It will be 
easy to do this without retaining air-bubbles. The thermometer 
is fastened by the short rubber tube, allowed a few minutes to 
reach the temperature of the inner liquid, the apparatus placed 
in the polarimeter and the reading quickly taken. It may be 
wrapped in some non-conducting material while waiting for the 
thermometer to reach its highest point. Observation with hot 
tubes should be made quickly; if a number are to be made, an 
interval of a few minutes should be allowed to intervene 
between each, during which the polarimeter trough should be 
opened. The delicate optical train may be injured by much 
heating. 

Sources of Light. — For white light, oil, gas, or electric lamps 
are employed, of which numerous patterns are furnished. Sat- 
isfactory results may be obtained by the Welsbach lamp. 
Wiley recommends the use of the acetylene flame, especially 
for deeply colored solutions. 

For monochromatic light, the lamp usually employed is 
a Bunsen burner with a ledge at the top for holding some 
solid sodium compound. A fused mixture of sodium chlorid 
and phosphate is better than sodium chlorid alone. The fol- 
lowing is an excellent method for obtaining a steady, strong, 
yellow light: Strips of common filter-paper 5 cm. wide and 
about 50 cm. long are soaked in a strong solution of sodium 
chlorid and thiosulfate, dried, and rolled into a hollow cylin- 
der of such size as to fit firmly on the top of the Bunsen 
burner. The cylinder is kept from unrolling by a few turns 
of fine iron wire. The flame burns at the top of the cylinder, 
giving for the first few minutes a luminous cone, but soon 
becoming pure yellow. The cylinder becomes a friable 
charred mass, but if not disturbed may be used for some time 
continuously or at intervals. 

Specific Rotatory Power. — The specific rotatory power of 
a substance is the amount of rotation, in angular degrees, 



20 FOOD ANALYSIS 

produced by a solution containing one gram of the substance 
in I c.c. examined in a column one decimeter long. It is 
usually represented by the symbol ['^]. To indicate the light 
employed in the observation, [«]d or [«]j is used, d stands for 
light of wave length corresponding to the D line of the solar 
spectrum (sodium flame) and j {jaune) for the transition tint. 
It is usual also to indicate in the same symbol the temperature 
of observation; thus, \_'^Yd' 

Under ordinary methods of observation the specific rota- 
tory power is represented by the following formula: 



[aJD = looa 



, , in which 
cl 



[a]jj is the specific rotaton- power for the light of the sodium flame, 
a is the angular rotation observed, 

c is the concentration expressed in grams per lOo c.c. of liquid, 
/ is the length of the tube in decimeters. 

Comparison oj Scales of Various Instruments. — Polarimeters 
are now usually provided with a scale reading to loo when 
a certain quantity of sucrose, called the normal weight, is 
dissolved in water and made up to loo c.c. For the German 
instruments, which are largely used in the United States, this 
is 26.048 grams. This scale is known as " Ventzke," "Schmidt 
and Hansch," and "sugar" scale. 

The instruments made by Schmidt and Hansch are gradu- 
ated to read correct percentages when the normal weight of 
sugar is contained in 100 Mohr's cubic centimeters and ob- 
served in a 2 decimeters tube at 17.5°. With the Laurent 
apparatus the normal weight, of the sugar should be contained 
in 100 true cubic centimeters. 

The volume of 100 Mohr's cubic centimeters is that of 
100 grams of water at 17.5° weighed in air with brass weights; 
it is equal to 100.234 true cubic centimeters. For the nor- 
mal weight of 26.048 grams in 100 Mohr's cubic centimeters 



SPECTROSCOPY 21 

of solution, may be substituted 25.9872 grams in 100 true 
cubic centimeters at 17.5°. 

At the session of the International Commission for Uniform 
Methods of Sugar Analysis held at Paris, July 24, 1900, it 
was agreed that the normal weight shall be fixed at 26 grams 
in 100 true c.c. at 20°, weighed in air with brass weights (see 
under "Sucrose"). 

The following factors may be employed for the conversion 
of data obtained by different instruments: 

I division Schmidt and Hansch 0.3468° angular rotation D. 

1° angular rotation D 2 .8835 divisions Schmidt and Hansch. 

I ° angular rotation D o. 7 5 1 1 division Wild . 

I division Laurent 0.2167° angular rotation D. 

I ° angular rotation D 4.6154 divisions Laurent . 

Correction for Precipitate. — In some cases the volume of 
precipitate produced by the clarifying agents is considerable, 
and a correction would be necessary. The error may be 
eliminated by Scheibler's method: A normal weight of the 
sample is dissolved in water or proper solvent, treated with 
the clarifying agent, the liquid made up to 100 c.c, shaken 
well, filtered, and a reading taken of the filtrate. A second 
portion of normal weight is treated in the same way except that 
it is made up to 200 c.c. before filtration. Great care must 
be taken in the readings. The true reading is obtained by 
dividing the product of the two readings by their difference. 

Spectroscopy. 

In practical analysis the spectroscope is mostly useful in 
detecting some of the rarer elements in ashes and water-resi- 
dues. For this purpose the direct vision instrument shown 
in figure 14 is sufficient. It will often serve for the examina- 
tion of absorption bands, but for precise research in distinguish- 
ing colors and specific absorptions a more elaborate instru- 
ment, as shown in figure 15, will be needed. Zeiss makes a 



22 



FOOD ANALYSIS 



direct vision instrument in which the h'ght enters by openings 

placed side by side, but forms 
spectra that are exactly super- 
posed. By this means a solution 
of known composition can be ex- 
amined in comparison with a 
material to be tested; or two 
flame-tests may be compared. 
This instrument can be mounted 
as shown in figure 14. 

For the examination of ashes 
or water-residues, the material is 
mixed with a few drops of hydro- 
chloric acid, a portion of the mass 
taken up on a loop of clean plati- 
num wire and held in a non-lumin- 
ous flame, the spectrum being ex- 
amined through the instrument. It 
is important that the first effects 
should be noted, as some sub- 
stances volatihze quickly. The 




Fig. 14. 



platinum wire should be cleaned by dipping it in a little pure 




Fig. 15. 



MICROSCOPY 23 

hydrochloric acid and heating it in the gas flame until it im- 
parts no color thereto. 

For the observation of absorption-bands of liquids, small 
flat bottles with ground and polished sides are used. These 
permit the observation of a thin or thick stratum as desired. 
Deeply colored solutions should not be used since large por- 
tions of the spectrum may be cut out by general absorption 
and the distinctive selective absorption be lost. 

For some purposes the microspectroscope will be needed, 
but its use is practically limited to medico-legal work. 

Fluorescence. 

This may be detected satisfactorily in the manner described 
by Allen: A test-tube or cylindrical beaker is nearly filled 
with a perfectly clear solution of the substance, set upon a 
dark surface, and observed from above. Another plan is to 
make a streak of the liquid on a piece of black glass or pol- 
ished black marble and examine this in a good white light. 
Tests can also be made by directing a ray of white light from 
any source through the side of a beaker containing the liquid 
and looking at it from above. In all the methods the liquid 
must be perfectly clear or misleading reflection-effects are pro- 
duced. 

Microscopy. 

For preliminary examination of food samples a hand lens 
is useful, but the practical analysis involves the use of the 
compound microscope. A good instrument can now be ob- 
tained at comparatively small cost. It should be supplied 
with at least two objectives, one of low power, about 16 mm. 
focus (f in.), and one of rather high power, 4 mm. focus 
(J in.). The usefulness of a microscope is much enhanced by 
the attachment of a sub-stage achromatic condenser and ad- 
justable diaphragm. Polarizing apparatus, including a selenite 
plate, is needed, especially for differentiation of starches. 



24 



FOOD ANALYSIS 



The instrument shown in figure i6, of American construc- 
tion, is arranged to receive all accessories. A double nose- 
piece will be sutlicient, as the high-power lens which is shown 




Fig. I 6. 



is not needed for chemical work. The outfit, with two lenses 
and polarizing attachment with selenite, costs about $70. 

For the better differentiation of objects submitted to ex- 
amination under the microscope, clearing and staining agents 
are used. In many cases details of structure are brought out 



MICROSCOPY 25 

sharply by using a dense liquid as a mounting fluid. The 
following is a list of the important apparatus and reagents: 

Slides and cover- glasses. 

Agate mortar, 2.5 cm. outside diameter, and a somewhat 
larger glass triturating mortar are useful for preparing mate- 
rials. The pestles of agate mortars are usually inconveniently 
short, and are much improved by being mounted in a wooden 
handle. 

Dissecting needles are easily made by sawing off the metal 
portion of an ordinary penholder close to the wood and for- 
cing the eye-end of a sewing needle under the ferrule which has 
been thus formed. A neat form of a needle-holder is furnished 
by the instrument makers. 

Small forceps and sharp scissors will be needed. 

Watch-glasses are used for immersing specimens in liquids; 
still better are the so-called Syracuse glasses, the best form 
of which has a ground-glass surface for memoranda. 

Water. Distilled water is best, but any clear, colorless 
water not containing much mineral or organic matter will 
answer. 

Glycerol. A pure article is easily obtained. 

Alcohol. The commercial 95 per cent, form is used for 
hardening tissues, but for ordinary microscopic work, a 70 
per cent, solution will suffice. 

Methyl alcohol in the purified form now obtainable may be 
substituted in many instances for common alcohol. 

Ether, chloroform, benzene, and carbon disulfid are occasion- 
ally used for their solvent action, especially to remove oils, 
waxes, and resins. Carbon tetrachlorid will be also of use. 
For these extractions it will often be most satisfactory to ope- 
rate in a small continuous extraction apparatus, with repeated 
washings, as described under "Extraction," drying the material 
at a gentle heat to remove all the solvent, which would inter- 
fere with the action of watery solutions or glycerol. 
4 



26 



FOOD ANALYSIS 



Chloral hydrate solution, — a saturated solution in water. 
Chloral hydrate and iodin solution, — a portion of the above 
solution to which a trace of iodin has been added. 

Potassium iodid and iodin solution, — potas- 
sium iodid, 0.4 gram; iodin, o.i gram; water, 
20 c.c. 
JkV-^l Zinc chloriodid and iodin solution: Dissolve 5 

£g^|Tjp||^ grams of zinc chlorid and 1.6 grams of potassium 
iodid in 17 c.c. of water and saturate with iodin. 

Sodium hydroxid, — 5 per cent, solution. In 
some instances a strong solution is employed, 
which is best prepared when required. 

Acid phloroglucol. This is best prepared 
when needed by dissolving a few milligrams of 
phloroglucol in i c.c. of alcohol and adding 
a drop of hydrochloric acid. 

Bottles (figure 17) with caps ground on and pipet, are the 
best for reagents. A little vasehn may be put on the joint to 
prevent sticking. 




Fig. 17. 



WATER AND FIXED SOLIDS 27 

CHEMICAL DATA 

Water and Fixed Solids (Extract). 

Water is usually determined with sufficient accuracy, pro- 
vided other volatile bodies are not present, by heating the 
material (solids should be finely divided) in a flat dish on the 
water-bath or in the water-oven until it ceases to lose weight. 
The residue constitutes the fixed solids or extract. Flat 
platinum dishes from 4 to 8 cm. in diameter and 0.5 cm. high 
are well adapted to this work. They should rest on porcelain or 
asbestos rings. Nickel dishes are often applicable, especially 
the broad shallow crucible covers made in dish form. Dishes 
of glass — especially the shallow (Petri) dishes used for microbe 
culture — and porcelain are suitable; aluminum and tin less 
so. In many cases drying will be facilitated by using an 
absorbent material such as pure quartz sand, powdered asbestos, 
or pumice-stone. These materials should be extracted with 
dilute hydrochloric acid, well washed, and well dried before use. 
The quantity used should be rapidly weighed, preferably in the 
dish in which the operation is to be carried out. It is advisable 
to cover the dish with a nearly flat, thin watch-glass in all the 
weighings. By a few trials a glass can be selected which fits 
fairly close to the rim of the dish and restricts evaporation or 
absorption of water. It is often convenient to weigh a small 
stirring-rod with the dish and absorbent. 

In many cases liquid can be measured directly into the 
dish, the residue being recorded in grams per loo c.c. or other 
suitable ratio. 

Sirupy and gelatinous liquids or those containing much solid 
matter, especially if this be somewhat difficult to dry, may 
often be more satisfactorily treated by diluting a weighed 
portion with several times its weight of water, evaporating a 
measured or weighed amount of the dilute liquid, and calcu- 
lating the amount of residue in the original substance. 



28 



FOOD ANALYSIS 



The ordinary water-bath and water-oven need no descrip- 
tion. The temperature of materials heated on the former is 
usually much less than ioo°; in the latter, slightly below 
ioo°. By using strong brine a somewhat higher temperature 
may be obtained. In the case of very hygroscopic or easily 




Fig. 1 8. 



decomposable bodies it may be necessary to dr}- in a current 
of hydrogen or at reduced pressure. 

Figure i8 shows a drying oven for use with a current of 
hydrogen. The apparatus was designed by Caldwell for 
determining moisture, ether-extract, and crude fiber as pre- 
scribed by the A. O. A. C, the three data being determined 
on the same sample. 



WATER ANB FIXED SOLIDS 29 

The bath is made of copper and is 24 cm. long, 15 high, 
and 8.5 broad. It stands in a piece of sheet-copper bent at 
right angles along the sides, as shown in the end view; on 
one side this vertical part need not be over i cm. high, just 
enough to project a little up the side of the bath, which rests 
snugly against it; along the other side it projects upward, at 
a little distance from the side of the bath, about 15 mm., and 
to about the height of 4 cm.; opposite each of the tubes of 
the bath a slot is cut in this vertical part, which serves then as 
a shoulder against which the glass tube rests when in place, to 
keep it from slipping down and out of position. 

The tube for containing the substance has at the zone a 
three small projections on the inner surface, which support 
a perforated platinum disk of rather heavy platinum foil carry- 
ing the asbestos filter. This tube is 13 cm. long and 23 mm. 
inner diameter, and weighs, with its closed stoppers, about 
30 grams. 

The filter is readily made in the same manner as the Gooch 
filter, the tube being first fitted to a suction flask by an en- 
largement of one of the holes of the rubber cork, or, better 
still, by slipping a short piece of rubber tube over it, of such 
thickness that it will fit tightly in the mouth of a suction flask 
provided with lateral tube for connection with the suction. A 
thin welt of asbestos is sufiicient; if it is too thick, the gas 
and ether will not flow through readily. 

About 2 grams of the substance are put in this tube, pre- 
viously weighed with the stoppers h and c, and the weight of 
the substance accurately determined by weighing tube and 
contents. The stoppers are removed, a band of thin asbestos 
paper is wound around the end d of the tube, a little behind 
the slight shoulder at the rim, as many times as may be neces- 
sary to make a snug fit, when this tube is slid down into the 
copper tube in the bath, thus preventing circulation of air 
between the glass and the copper tubes that would retard tlic 



30 FOOD ANALYSIS 

heating of the former; the stopper e is put in the lower end 
of the tube for connection with the hydrogen supply, and the 
stopper / in the upi)er end; this latter stopper is connected 
by rubber tube with a glass tube slipping easily through one 
of the holes of a rubber cork closing a small flask containing 
a little sulfuric acid, into which this tube just dips; when as 
many tubes as are to be charged are thus arranged in place and 
the hydrogen is turned on, the even flow of the current through 
the whole number is secured by raising or lowering a ven* little 
the several tubes through which the outflow passes, so as to get 
a litde more back pressure for one, or a little less for another, 
as may be found necessary. When the drying.is supposed to be 
completed, the tubes are weighed again with their closed 
stoppers, and so on. 

For ether-extraction the imstoppered tube with contents is 
put directly into the extractor. 

Carr and Osborne have made an extended series of inves- 
tigations as to the determination of water, and find that more 
accurate results may be obtained if the operation be conducted 
under a diminished pressure at a temperature not exceeding 
70° C. Under these conditions it was found p>ossible to dehy- 
drate levulose completely, without decomposition. The oven 
is made of a section of metal tubing, from 15 to 20 cm. in 
diameter and 30 to 40 cm. long. One end is closed air-tight 
by a brass end-piece, brazed or attached by a screw. The 
other end is detachable and is made air-tight by ground surfaces 
and a soft washer. On the top are apertures for the insertion of 
a vacuum-gauge and for attachment to a vacuum-apparatns, 
thermostat and thermometer. The aperture for admission of 
air or hydrogen is best placed at the fixed end. The oven may 
be heated by a single burner, but a series of small jets is prefer- 
able. The metal should be protected by sheet asbestos. The 
temperature of the oven can be kept uniform by a gas regulator, 
or by attention to the lamp. 



WATER AND FIXED SOLIDS 3 1 

The method of operating is as follows: Clean pumice-stone 
of two grades of fineness is used, one that just passes through 
a I mm. mesh and one that passes through a 6 mm. mesh. 
These are digested with hot 2 per cent, sulfuric acid, washed 
by decantation until the wash-water is free from acid, placed, 
wet, in a sand crucible and heated to redness. When the 
water is expelled, the material may either be placed hot into a 
desiccator or directly into the drying dishes. In loading the 
dishes, place a thin layer of dust over the bottom of the dish 
to prevent the material to be dried from coming in contact 
with the metal ; over this layer place the larger particles, nearly 
filling the dish. If the stone has been well washed, no harm 
may result from placing the dish and stone over the flame for a 
moment before transferring to the desiccator preparatory to 
weighing. 

If the material to be dried is dense, it is diluted until the 
specific gravity is in the neighborhood of 1.08 by dissolving a 
weighed quantity in a weighed quantity of water. (Alcohol 
may be substituted in material not precipitable thereby.) Of 
this, 2 to 3 grams may be distributed over the stone in a dish 
the area of which is in the neighborhood of 20 sq. cm., or one 
gram for each 7 sq. cm. of area. The material is distributed 
uniformly over the pumice by means of a pipet weighing- 
bottle (weighing direct upon pumice will not answer), ascer- 
taining the weight taken by difference. 

The dishes are placed in the vacuum-oven, which should be 
m^ntained at a pressure of not more than 125 mm. of mer- 
cury. The temperature must not exceed about 70°. All 
weighings must be taken with the dish covered by a close-fitting 
plate. The open dish must not be exposed to the air longer 
than absolutely necessary. Weighings may be made at inter- 
vals of two or three hours. 

In the laboratory of the United States Geological Survey a 
sheet-iron or nickel basin about 10 cm. in diameter and 3 



32 FOOD ANALYSIS 

cm. deep is set upon an iron plate which is heated directly by 
the burner. A platinum or pipe-clay triangle rests in the 
basin and supports the dish containing the hquid to be evap- 
orated. It is stated that almost any liquid can be evaporated 
in this way without sputtering. The temperature, however, is 
liable to be too high for many organic bodies. 

Parsons has obtained good results in the drying of sensitive 
organic substances by the following method: A perfectly 
neutral petroleum oil, free from animal or vegetable oils and 
mineral substances, sp. gr. 0.920, flash test 224°, fire test 260°, 
boihng-point about 288°, is heated to about 120° for some time 
and preserved in a well-stoppered vessel. A quantity of oil 
about six times that of the weight of the substance to be dried 
is heated in an evaporating dish in a drying oven to a tempera- 
ture of 1 1 5°, and then weighed. The weighed portion of the sub- 
stance is put into the oil; if it be very moist, it is added in small 
portions. Slight effervescence will usually occur, and the mass 
should be kept in the drying oven for a short time after effer- 
vescence has ceased. The evaporating dish containing the oil 
and substance is weighed; the loss is moisture. The whole 
operation may be completed in less than half an hour. 

Nitrogen. 

Total Nitrogen. — The Kjeldahl-Gunning method is the 
most satisfactory. 

The reagents and operation are as follows : 

Potassium Sulfate. A coarsely powdered form free from 
nitrates and chlorids should be selected. 

Sulfuric Acid. This should have a sp. gr. 1.84 and be free 
from nitrates and ammonium. 

Standard Acid. \ Sulfuric or hydrochloric acid, the strength 
of which has been accurately determined. 

Standard Alkali. ' Ammonium hydroxid, sodium hydroxid, 



NITROGEN 33 

or barium hydroxid, the strength of which in relation to the 
standard acid must be accurately determined. 

Strong Sodium Hydroxid Solution. 500 grams should be 
added to 500 c.c. of water, the mixture allowed to stand until 
the undissolved matter settles, the clear liquor decanted and 
kept in a stoppered bottle. It will be an advantage to de- 
termine approximately the quantity of this solution required 
to neutralize 2o-c.c. of the strong sulfuric acid. 

Indicator. Cochineal solution is recommended by the A. 
O. A. C, but methyl-orange and azolitmin are satisfactory. 
Phenolphthalein is not well adapted to titration of ammonium 
compounds. (See under ''Indicators.") 

Digestion Flasks. Pear-shaped round-bottomed flasks of 
hard, moderately thick, well-annealed glass, about 22 cm. 
long, maximum diameter of 6 cm., tapering gradually to a 
long neck, 2 cm. in diameter at the narrowest part, and slightly 
flared at the mouth. 

Distillation Flasks. Jena-glass flasks of about 550 c.c. ca- 
pacity. A copper flask, such as sometimes used in the manu- 
facture of oxygen, may be substituted. 

Combined Digestion and Distillation Flasks. Jena-glass 
round-bottomed flasks with a bulb 12.5 cm. long and 9 cm. in 
diameter, the neck cylindrical, 15 cm. long and 3 cm. in di- 
ameter, flared slightly at the mouth. 

Process. 0.7 to 3.5 grams, according to the proportion of 
nitrogen, are placed in a digestion flask. Then 10 grams of 
powdered potassium sulfate and 15 to 25 c.c. (ordinarily about 
20 c.c.) of the strong sulfuric acid are added and the digestion 
conducted as follows: The flask is placed in an inclined posi- 
tion and heated below the boiling-point of the acid for from five 
to fifteen minutes, or until frothing has ceased. Excessive 
frothing may be prevented by the addition of a small piece of 
paraflin. The heat is raised until the acid boils briskly. A 
small, short-stemmed funnel may be placed in the mouth 



34 



FOOD ANALYSIS 



of the flask to restrict the circulation of air. No further atten- 
tion is required until the liquid has become clear and colorless, 
or not deeper than a pale straw. 

When Kjeldahl operations are carried out in limited number, 
the arrangement used in the laboratory of one of us (L) has been 
found very satisfactory. A double-Y, terra cotta drain-pipe, 
about 20 centimeters internal diameter, is connected by an elbow 
directly with the chimney-stack. The dige^ion flasks are 
supported as shown in the rough sketch, figure 20 (not drawn 
exactly to scale). Two flasks can be operated at once. The 





Fig. 19. 



Fig. 20. 



central opening is convenient for other operations producing 
fumes. Openings not in use are closed by circles of heavy 
asbestos. 

The apparatus shown in figure 19 is used when many de- 
terminations are made. As corrosive vapors are given ofif, 
it must be placed under a hood. The central opening in 
the ventilating pipe shown in figure 20 will be satisfactory; the 
mouths of the flasks should be well inside the margin of the pipe. 

When the liquid has become colorless or very light straw 



'' NITROGEN 35 

yellow, it is allowed to cool, diluted with loo c.c. of water if the 
smaller form of flask has been used, the liquid transferred to the 
distilling flask, and the digestion flask rinsed with two portions 
of water, 50 c.c, each, which are also transferred to the distilling 
flask. With the larger form of flask the dilution is made at once 
by the cautious addition of 200 c.c. of water. Granulated zinc, 
pumice stone, or 0.5 gram of zinc dust is added. 50 c.c. of the 
strong sodium hydroxid solution, or sufficient to make the 
reaction strongly alkaline, should be slowly poured down the side 
of the flask so as not to mix at once with the acid solution. 
It is convenient to add to the acid liquid a few drops of phenol- 
phthalein or azolitmin solution, to indicate when the liquid is 
alkaline, but it must be noted that strong alkaline solutions 
destroy the former indicator. The flask is shaken so as to 
mix the alkaline and acid liquids and at once attached to the 
condensing apparatus. The receiving flask should have been 
previously charged with a carefully measured volume of the 

-^ acid (100 c.c. is a convenient amount). The distillation is 
conducted until about 150 c.c. have passed over. The acid is 
then titrated with standard alkali and methyl orange, cochineal, 
or azolitmin, and the amount neutralized by the distilled am- 
monium hydroxid determined by subtraction. Each c.c. of -7- 
acid neutralized is equivalent to 0.007 nitrogen. 

The distillation in this operation requires care, as the amount 
of ammonium hydroxid is determined by its neutralizing power, 
hence solution of the alkali of the glass will introduce error. 
Common glass is not satisfactory. Block-tin is the best 
material for the Kjeldahl- Gunning form, but Moerrs has shown 
that it is not adapted to the methods in which mercury oxid 
is employed. He found that Jena-glass tubes resist the action of 
the ammonium hydroxid. 

The most satisfactory condensing arrangement for general 
laboratory use is a copper tank of good size, through which 



36 



FOOD ANALYSIS 



several condensing tubes pass. Such an arrangement is shown 
in side-view in figure 26. A more detailed view of the con- 
struction as applied to Kjeldahl distillations is shown in figure 
21, which is a rough sketch, not drawn to scale. The flask is the 
standard Jena-glass distilling flask, about 12 cm. diameter, the 
tank should be high enough to allow of a condensing tube 60 
cm. long. The connection of this with the receiving flask is 
made by means of a bulb tube to allow for occasional drawing- 
back of the liquid. The cork 
through which this tube passes 
into the flask must not fit closely, 
as opportunity must be given for 
expansion of the air. The safety 
tube connecting the distiUing 
flask with the condenser should 
terminate a little below the water 
level in the tank. The apparatus 
may be satisfactorily heated by 
the low temperature burner, as 
shown in figure 31. To avoid 
spurting of the boiling liquid, it 
is usual to interpose a safety-tube 
between the distilling flask and 
the condenser. Many forms 
have been suggested. Those 
shown in figures 22 and 23 are most in use. Figure 23 is the 
more complex, but is satisfactory. The distillation will be 
hastened if this tube be covered with non-conducting material. 
In some determinations (as in pepper) the Kjeldahl- Gunning 
method must be replaced by Arnold's modification: i gram of 
the sample is mixed with i gram of crystallized copper sulfate 
and I gram of mercuric oxid. The potassium sulfate-sulfuric 
acid mixture as given above is added and the mass heated 
cautiously until frothing ceases, when the temperature is raised 




Fig. 21. 



NITROGEN 



37 



and the digestion completed. The liquid is diluted for dis- 
tillation, 50 ex. of a solution of commercial potassium sulfid 
(40 grams to 1000 c.c.) are added, and sufficient sodium hy- 
droxid as usual. The liquid is liable to bump. 

Modification for Nitrates. If nitrates are present in the 
material, the weighed sample is well mixed with 35 c.c. of 
sulfuric acid containing 2 per cent., by weight, of salicylic acid, 
and the mass shaken frequently during ten minutes ; 5 grams of 
sodium thiosulfate are added and 10 grams of potassium sulfate. 





Fig. 22. 



Fig. 23. 



The mixture is heated very gently until frothing ceases and then 
according to the usual method. The nitrogen in the distillate 
will include that derived from the nitrogen of the nitrates. 

Albuminoid Nitrogen. — Stutzer's method for this deter- 
mination requires a special reagent: 

Copper Hydroxid Mixture. 100 grams of copper sulfate 
are dissolved in 5000 c.c. of water, 25 c.c. of glycerol added, 
and then a dilute solution of sodium hydroxid until the liquid 
is alkaline. The mass is filtered, the precipitate is mixed well 
with water containing 5 c.c. of glycerol per 1000 c,c. and 



38 FOOD ANALYSIS 

washed until the washings are no longer alkaline. It is then 
rubbed up with a mixture of 90 per cent, water and 10 per 
cent, glycerol in sufficient quantity to obtain a uniform magma 
that can be measured with a pipet. The quantity of copper 
hydroxid per c.c. should be determined. It should be kept 
in a well-closed bottle. 

Analytic Method. A suitable amount of the material, gen- 
erally about 0.7 gram, is heated with 100 c.c. of water to 100°, 
and a quantity of the copper hydroxid mixture containing 
about 0.5 gram of solid added, stirred well, allowed to cool, 
filtered, washed well with cold water, and the filter and pre- 
cipitate treated by the Kjeldahl- Gunning method. 

Substances rich in starch are best subjected to about ten 
minutes' warming in the water-bath instead of direct boiling. 
With substances containing much phosphate a few cubic 
centimeters of alum solution should be well stirred in before 
adding the copper hydroxid. 

Crude Fiber. 

The A. O. A. C. method is substantially as follows: 2 grams 
of the substance, well extracted with ether (see under "Ex- 
traction"), are mixed in a 500 c.c. flask with 200 c.c. of boiling 
water containing 1.25 per cent, of sulfuric acid; the flask is 
connected with an inverted condenser, the tube of which passes 
only a short distance below the rubber stopper of the flask. 
The liquid is brought to the boiling-point as rapidly as possible 
and maintained there for 30 minutes. A blast of air conducted 
into the flask may serve to reduce the frothing of the liquid. 
The mass is filtered, washed thoroughly with boiling water 
until the washings are no longer acid; the undissolved sub- 
stance rinsed back into the same flask with the aid of 200 c.c. 
of boiling water containing 1.25 per cent, sodium hydroxid, 
nearly free from sodium carbonate; again brought to the 
boiling-point rapidly and maintained there for 30 minutes as 



ASH 39 

directed above. The liquid is filtered by means of a Gooch 
crucible; washed with boiling water until the washings are 
neutral to phenolphthalein ; dried at iio°; weighed and incin- 
erated completely. The loss of weight is crude fiber. 

The filters used for the first filtration may be linen, glass, 
wool, asbestos, or any form that secures clear and reasonably 
rapid filtration. Hardened-paper filters may serve. The sul- 
furic acid and sodium hydroxid must be made up of the specified 
strength, determined by titration. 

Some analysts use stronger solutions. Hehner used 5 per 
cent, acid and alkali. It would be convenient if normal sul- 
furic acid and normal sodium hydroxid were adopted as solvents. 
It is probable that carbon tetrachlorid could be advantageously 
substituted for ether in the preliminary extraction. 

Crude fiber should not be called cellulose. 

Ash. 

The ash of food materials may usually be determined by 
heating several grams in a platinum or porcelain crucible at a 
low red heat. Higher temperature may cause loss of volatile 
salts — e. g., chlorids. If a white ash cannot be obtained thus, 
the material should be heated only to a temperature sufficient 
to produce charring, the charred mass thoroughly extracted 
with water, and the insoluble matter collected on a filter, 
which may then be returned to the crucible and ashed. To 
this residue the filtrate containing the soluble matter is now 
added, the liquid evaporated to dryness, heated to low red- 
ness, cooled, and weighed. 

A muffle, heated by gas, will often be very useful in the 
incineration of organic bodies. A light draught of air should 
be maintained during the operation. 

Ash Soluble in Water. — The ash obtained as above is treated 
with boihng water, the solution filtered through an ashless 
filter, and the filter and contents again ignited and weighed. 



40 FOOD ANALYSIS 

The soluble ash is determined by difference. If desired, the 
filtrate may be filtered to dryness, heated just below redness, 
and weighed. The first method is the most convenient. 

Alkalinity oj ash is often an important datum. It will differ 
with the indicator used and whether tested by direct titration 
or upon the portions soluble and insoluble in water. The 
following method will furnish data of value in many cases. 

The ash is mixed with water, heated nearly to boiling, filtered 
and washed until the filtrate measures about 50 c.c. An in- 
dicator (phenolphthalein is usually employed) is added to the 
filtrate titrated to neutrality with ^ hydrochloric acid. Methyl 
orange is added and the titration carried to neutrality again. 
The filter and contents are dried, ignited, and added to the 
residue in the dish. Excess of standard acid and methyl 
orange are added and the material titrated to neutrality with 
sodium hydroxid. 

It is often sufficient to titrate the ash directly, using a single 
indicator and not separating the portions soluble and insoluble 
in water. In this case azolitmin may be satisfactory. 

Ash Insoluble in Acid. — The residue insoluble in water is 
treated with hydrochloric acid and the portion undissolved 
is well washed on the filter with water, dried, ignited, and 
weighed. 

The ash of jats is conveniently determined by the following 
method : A weighed quantity is melted in a platinum dish, and 
a smaller filter, free from ash, is folded in four, placed upright 
in the melted fat, and hghted. The fat is quickly burnt off. 

The following is a compilation of methods proposed for the determination 
of the ash of sugars, molasses, honeys: 

(i) 5 to 10 grams of the material are heated in a platinum dish of from 50 to 
100 c.c. capactiy at 100° until the water is expelled, and then slowly over a flame 
until intumescence ceases. The dish is placed in a muffle and heated at low red- 
ness until a white ash is obtained. If the substance contain iron or any other 
metal capable of uniting with platinum, a dish of some other material must be 
used. For soluble ash the ash obtained as above is digested with water, filtered 



EXTRACTION WITH MISCIBLE SOLVENTS 4 1 

through a Gooch crucible, washed with hot water, and the residue dried at 100° 
and weighed. The difference of weights equals the soluble ash. 

(2) To 25 grams of molasses or 50 grams of sugar, 50 mg. of zinc oxid are 
added, and the mass incorporated thoroughly by adding dilute alcohol and mix- 
ing. It is then dried and ignited as above. The weight of zinc oxid is deducted 
from the weight of the ash. 

(3) The mass is carbonized at low heat, the soluble salts dissolved with hot 
water, the residual mass burned, the solution of soluble salts added, and evapo- 
rated to dryness at 100°, ignited gently, cooled in a desiccator, and weighed. 

(4) The sample is saturated with sulfuric acid, dried, ignited gently, then 
burnt in a muffle at low redness. One-tenth of the weight of the ash is deducted 
to calculate the percentage. 

Extraction with Miscible Solvents. 

For thorough extraction, especially with difficultly soluble 
materials and volatile solvents, the continuous extraction ap- 
paratus devised by Szombathy, but commonly called the Soxhlet 
tube, is most suitable. 

The apparatus, as shown in figure 24, is provided with a 
globular metal condenser, but any form may be employed. The 
material may be placed in a fat-free paper thimble and covered 
with a plug of cotton to prevent loss of fine particles. In place 
of the cotton plug a Gooch crucible may be used, as shown in the 
cut. The top of the thimble should be a short distance below, 
and the top of the crucible a short distance above, the bend of 
the siphon. The thimble should be supported by a section of 
glass tubing, i to 2 cm. long, with rounded edges; the edge 
on which the thimble rests should be a little uneven to prevent 
a close joint, which would hinder the siphoning of some of the 
liquid. 

Another method is to use a glass tube open at both ends, the 
material to be extracted being held in position by loose plugs of 
cotton placed above and below. 

Loss of solvent by leakage often occurs. It may be dim- 
inished somewhat by soaking the corks in rather strong hot 
gelatin solution, draining them quickly and then exposing them 
for some hours to formaldehyde vapor. 
5 



42 



FOOD ANALYSIS 



The solvents most generally employed are ether and petro- 
leum spirit, but chloroform, carbon tetrachlorid, carbon disulfid, 

benzene, acetone and absolute alcohol 
have special applications. Carbon tet- 
rachlorid is well adapted for extraction 
purposes as it has high solvent power 
and is not easily inflammable. 

When extraction is completed, the 
carton and materials may be removed 
from the tube, and, replacing the parts of 
the apparatus, much of the solvent may 
be redistilled into the extractor, thus 
recovering the liquid. Care must be 
taken not to distil the contents of the flask 
closely or heat strongly, lest some of the 
more volatile of the dissolved matters 
pass into the distillate. 

The tedious process of extraction may 
often by replaced by direct solution as 
follows: A convenient amount of the 
material, finely powdered, is placed in a 
flask, a definite volume of solvent, (e. g. 
loo c.c.) poured on, the flask tightly 
corked, the mixture gently shaken at 
convenient intervals for some hours, and 
allowed to remain in overnight. Care 
must be taken that the solvent does not 
come in contact with the cork. The mix- 
ture, after standing, is again shaken a 
few times, allowed to settle somewhat and 
an aliquot part (e.g. 50 c.c.) rapidly filtered 
ofi^, evaporated as usual and weighed. 
The process is adapted for use with shghtly volatile solvents 
such as alcohol, but with care may be used with ether, petroleum 



Fig. 24. 



EXTRACTION WITH IMMISCIBLE SOLVENTS 



43 



spirit, and carbon tetrachlorid. It has value as a sorting 
method. 



Extraction with Immiscible Solvents.- 

Solvents not miscible with water are employed for extracting 
substances by shaking the solvent thoroughly with the aqueous 
solution, allowing the liquids to 
separate, and removing one of them. 
The process is most conveniently 
performed in a stoppered separator. 
The principal difficulty is the liabil- 
ity of some liquids to form emulsions 
which separate only after long stand- 
ing. Separation may sometimes be 
hastened by cooling the mixture or 
by adding more of the solvent. One 
of the most satisfactory methods 
when operating upon small amounts 
of liquid is to whirl the mixture for 
a short time in a high-speed centri- 
fuge. 

Figure 25 shows a special appa- 
ratus for use with solvents lighter 
than water. 

The cylinder A should hold about 
1000 c.c. Two openings are not 
necessary, since both tubes may pass 

through the cork, but the arrangement shown is more convenient. 
600 c.c. of the solution are placed in the cylinder, 300 c.c. of 
solvent added and the mixtures well shaken. The rest of the 
apparatus is then attached. The flask B has a capacity of 200 
to 300 c.c; the solvent in it is heated by a water-bath. The 
vapor passes by a into b, the condensed liquid flows to the 
bottom of A and rises through the solution; the upper layer 




Fig. 25. 



44 



FOOD ANALYSIS 



returns through c into B. The tube c should not extend into the 
Hquid in B. A small quantity of aqueous liquid may collect at 
intervals in B and should be removed. 

Distillation and Sublimation. 

Retorts and alembics are now but little used, but are service- 
able in some cases. With glass vessels the irregular percussive 
boiling, commonly called "bumping," is liable to break the 




Fig. 26. 



vessel or to spurt portions of the undistilled Hquid into the con- 
densing apparatus. This may often be prevented by the ad- 
dition of a fev^ fragments of pumice, clay pipe, or platinum foil. 
Dry pumice floats on most liquids. It may be made to sink 
either by soaking it in water for a day or so or by heating the 
fragment to redness and quenching it in the liquid. With 



DISTILLATION AND SUBLIMATION 45 

inflammable liquids, the latter method must be used cautiously. 
Bumping may often be prevented by using the burners shown 
in figures 31 and 32. 

Condensing apparatus is made in considerable variety; 
Glass and block-tin are the materials for tubes. The glazed 
porcelain tubes made for pyrometers would probably be well 
adapted for straight condensing tubes. Glass tubes are liable 
to crack at the point at which the cooling action begins. To 
avoid leakage and the contact of hot vapors with corks or 
rubber tubes, the connections should be as few as possible. Fig- 
ure 26 show^s a copper tank through which the condensing tube 
passes. This apparatus is especially adapted to the so-called 
"ammonia" process for water- analysis. The neck of the 
retort being inclined slightly, as shown, causes any material 
thrown into it to return to the boiling liquid. 

Figure 27 shows an improved form of distilling apparatus 
devised by R. S. Weston. The condenser tube is of copper 
or japanned galvanized iron. The details of construction and 
arrangement are sufficiently indicated in the drawing. The 
apparatus is shown as arranged for water analysis. When 
Kjeldahl distillations are being made the lower end of the 
block-tin tube should be extended by means of a bulbed glass 
tube, as noted elsewhere. Safety bulbs may also be placed 
between the flask and condensing tube in such a way as to 
avoid rubber-tube connections. Materials are added by 
means of long-stemmed funnels. Weston uses a Bunsen 
burner, but it is probable that the burners figures 31, 32, would 
be more satisfactory. 

Figure 28 shows Cribb's condenser, which may be attached 
to any distilling apparatus. The distillation tube is attached 
at A. The walls are double; condensation occurs in the space 
between them, and the distillate flows out by the tube E. The 
cooling water flows through F to the bottom of the inner space, 
overflows at J into the catch-basin below, escaping by G. 



46 



FOOD ANALYSIS 



The stopper I serves to steady the tube P, and should have 
several large notches cut in it to allow the water to escape freely. 
It is usually necessary to wrap a piece of muslin around the 



C/a/rr/o 



St^/yjoor/^ rj 



C/a/rr/ 




YlG. 27. 



outside of the apparatus to cause the overflowing water to run 
properly. The condenser may be made of glass, block-tin, 
or tinned copper. Experience shows that the apparatus will be 



DISTILLATION AND SUBLIMATION 



47 



more satisfactory if some of the dimensions are changed from 
those indicated in the figure, which is taken from Cribb's paper. 
The annular space should be larger, especially at the bottom; 
the catch-basin must be roomy, and G should have a caliber 
at least three times that of F. The catch-basin is held in place 
by rubber tubing. The condenser is supported by a strong 
clamp. L is for attachment of an air-pump for distillation 
under diminished pressure. 

Distillation of small amounts of material may be made 
with the ordinary extractor, terminating 
the operation before the distillate reaches 
the level of the bend of the siphon. 

For many distillations the simple appa- 
ratus shown in connection with determin- 
ation of the volatile acids of butter will 
serve, but a side-neck flask, as shown 
in figure 29, is more generally useful. 
In this figure the condensing tube is 
represented relatively too short; for the 
volatile bodies encountered in food anal- 
ysis the condenser should be at least 50 
cm. long. This form of flask permits of 
introduction of materials without discon- 
necting the apparatus and also of distilla- 
tion in a current of steam or of indifferent 




Z> 



F 



C 



D 



, 3 




gas. 



Fig. 28. 



For distillation in a current of steam, a 
generator is needed. A Jena flask of good size is most con- 
venient. It should be provided with a stopper with two 
tubes, one about 0.5 cm. caliber, reaching to near the bottom 
of the flask, the other about i.o cm. caliber, reaching just 
below the level of the stopper. The latter is connected with a 
tube passing nearly to the bottom of the side-neck flask. The 
smaller tube in the generator is for safety in case of obstruc- 



48 



rOOD ANALYSIS 



tion. Its upper opening should be directed so that no damage 
will be done if the hot liquid is thrown out. 

With steam distillation, a moderate heat should be maintained 
under the distillation flask, and the water in the generator kept 
boihng actively. The junction between the two flasks should 
be by tubes which touch as closely as possible, held by a rubber 
sleeve. 




Fig. 29. 

Inverted Condenser. — For prolonged boiling in water without 
concentration, the simplest arrangement is a flask fitted with a 
cork carrying a tube about 2 meters long. The lower end 
should be cut off obhquely. If the boiling is moderate, the 
vapors will condense and run back. For volatile Hquids or 
special cases, regular condensers are used. The ordinary 
straight form, made of glass, is usually employed, but the ball- 



APPARATUS AND CHEMICALS 49 

form, shown in figure 24, is compact. This can be obtained of 
glass. 

Fractional distillation is best carried out with the bulb-tubes 
devised for attachment to ordinary flasks so that the vapor may 
be partially condensed and succeeding portions washed with 
the liquid which runs back continuously into the flask. The 
most used are the Le Bel-Heninger and Glynsky tubes. The 
former bears from two to six bulbs. The upper part has an 
inclined side tube for connection with the receiver and an 
opening through which the thermometer can be passed. Each 
of the bulbs is connected with the one just below by a side tube. 
At the constricted part of each bulb a small thimble of platinum, 
copper, or nickel gauze rests. The vapor condenses in the 
cups and washes the vapor subsequently formed. The liquid 
runs off from each bulb, back to the flask. The flame should be 
regulated so as to keep all the cups full, and cause the distillate 
to fall from the end of the tube in separate drops. In the 
Glynsky bulb, glass balls replace the gauze. 

The United States revenue-law requires all distilling ap- 
paratus to be registered, no matter for what purpose it is used. 
Heavy penalties are imposed for using non-registered stills. 
No fee is imposed for registry, which is made on blanks furnished 
by the Collector of Internal Revenue. 

Sublimation may be performed in a narrow test-tube or 
watch-glasses with concavities facing, the upper glass being 
slightly small so that it may fit well. A gentle heat is applied 
to the lower dish. By substituting a beaker containing water 
for the upper watch-glass a better cooling effect will be ob- 
tained. 

Apparatus and Chemicals. 

These can now be obtained generally of good quality at 
almost all times and places, but a few suggestions may be of 
value. 





FOOD ANALYSIS 



Centrijugc. — Centrifugal apparatus is of much advantage in 
laboratory work. The slow-speed machines made for milk 
analysis are of limited application; much better results are 
obtained by the high-speed apparatus of the type shown in 
figure 30. 

In operating such machines, the load on the revolving arms 
must be balanced or the center of gravity will not coincide 

with the center of revolution, and 
an objectionable vibration will be 
produced. The machine should be 
attached to a firm table or shelf arid 
kept properly oiled and protected 
from dust. The tubes usually fur- 
nished are narrowed at the bottom, 
and, as solid material is apt to be 
packed closely by the centrifugal 




action, it is sometimes difficult to 
dislodge it, but care should be taken 
to get all such material out of the 
tube so as not to contaminate the 
substance used in a subsequent ex- 
periment. If it be desired to use 
vessels not narrowed at the base, 
small glass tubes closed by cork at 
one end may be substituted. In 
Fig. 30. this case, however, the lower end 

of the tube-holder should be packed 
with cotton to such a height that the cork cannot be driven into 
a part of the tube narrow enough to hold it tightly. If this 
precaution be neglected, the rotation will push the glass tube so 
far into the tube-holder that it may be impossible to draw it out 
without leaving the cork. 

Glassware suitable for most laboratory work is now made 
in the United States, but the Bohemian and Jena glass still 



APPARATUS AND CHEMICALS 5 1 

shows important merit which will lead to preference for it in 
many cases. For the cleaning of glass and porcelain, espe- 
cially when working with fatty matters, the commercial triso- 
dium phosphate is of much use. Vessels cleaned with it must 
be well rinsed. A bath of so-called battery fluid (potassium 
dichromate or sodium dichromate, or, better, the crude chromic 
acid sold for the purpose, 250 grams; water, 2000 c.c; sul- 
furic acid, 300 c.c.) will make an efficient cleaning solution for 
all non-metallic articles. These should be cleansed with soap, 
sodium phosphate, or sodium carbonate to get rid of the greasy 
matters, rinsed, and then soaked in the liquid overnight. The 
solution gives off no fumes and its color guards against imperfect 
rinsing. It is of little value when it has become brown or 
green, but may be freshened by adding crude chromic and 
sulfuric acids. As the liquid is very corrosive, all waste from 
it should be washed down the drain-pipes with a free flow 
of water. Strong sulfuric acid is used by some chemists, 
especially for cleaning greasy apparatus. Organic materials 
such as corks and rubber tubes should, of course, not be put in 
these cleaning solutions. 

For heating beakers and fiat-bottomed flasks the hot-plate 
is much used, but the thin cast-iron plates commonly furnished 
are unsatisfactory. A better form is a rolled plate at least i 
cm. thick. Nickel wire-gauze is a good substitute for the 
common wire-gauze. The Chaddock burner, made of non- 
corrodable materials, is now obtainable, and is adapted to use 
in the fume-box. Electric heating apparatus has been brought 
to considerable efficiency, and will in time supplant all present 
methods, but the installation and operation are as yet costly. 
An incandescent lamp may be arranged as a heating apparatus, 
and is especially satisfactory in extractions and distillations 
with inflammable materials. The low-temperature burner and 
evaporating burner shown in figures 31 and 32 are convenient in 
many operations, especially in heating liquids liable to bump. 



52 



FOOD ANALYSIS 



The inlet of the former is too short; it should be lengthened 
by a piece of metal tube, or the rubber connection will become 
hot. In default of this lengthening the joint may be kept cool 
by wrapping around it a piece of muslin, the ends of which dip 
in a vessel containing water. 

Filter-papers are furnished in great variety, adapted to all 
purposes. The so-called hardened filters are serviceable in 
several operations, such as determination of crude fiber, insolu- 
ble matter, and extraction with volatile solvents, for with care 
the wet precipitate can be scraped off without removing an 
appreciable amount of the filter-paper. Slightly flattened 





Fig. 31. 



Fig. 32. 



glass rods or round rods bent at the middle to an obtuse angle 
are convenient because they are not liable to roll off of beakers 
or funnels. 

Reagents, especially those used only in small amounts, are 
most conveniently kept in capped bottles, each with small glass 
tube or pipet, the tube being long enough to reach above the 
top of the bottle (figure 17). In this way the solution will not get 
in contact with the neck of the bottle. Solids should be kept in 
hood-stoppered bottles, — i. c, those in which the flat top of the 
stopper is close to the bottle, — so as to give less chance for de- 
posit of dust. All chemicals in general use should be kept in 
closed cases, ammonium hydroxid and ammonium carbonate 



APPARATUS AND CHEMICALS 53 

being separate from the common acids. The stock bottles for 
acids and standard solutions should be protected from dust 
by placing over the stopper of each, an inverted tumbler large 
enough to rest on the top of the body of the bottle. 

Platinum ware requires care to prevent staining and crack- 
ing. Substances containing any of the easily-reducible metals 
must not be heated in contact with platinum; even iron com- 
pounds in the presence of reducing agents — e. g., filter-paper — 
will do harm. Sudden cooling of platinum should be avoided, 
as it tends to make the metal brittle. After being heated to 
redness the metal, when cold, should be lightly rubbed with 
very fine sea-sand (not river-sand nor powdered quartz or 
pumice), by which the metal will be burnished and its texture 
preserved. The platinum-pointed forceps should be treated 
in the same way. 

Platinum dishes may often be cleaned by rubbing them 
with sodium amalgam, decomposing this by immersion in 
water, and driving the mercury off by heating to redness. 
Some stains may be removed by melted potassium acid sulfate. 

Nickel dishes may be substituted for platinum in cases in 
which only gentle heating is required, but nickel is apt to be 
injured by direct heating with gas. 

For lubrication of glass stopcocks, the following mixtures, 
devised by Phillips, are useful : 

Pure rubber, 70 parts Pure rubber, 70 parts 

Spermaceti, 25 " Unbleached beeswax, ... 30 " 

Vaselin, 5 " 

The rubber must be fresh and pure; rubber scraps will not 
answer. It should be melted in a covered vessel, the other 
materials added, and the mixture well stirred while hot, care 
being taken not to scorch it. It must not be exposed to air 
longer than is necessary during heating, and should be kept 
in well-closed bottles. These mixtures may be removed from 



54 FOOD ANALYSIS 

stopcocks by a little strong nitric acid which loosens the lubri- 
cant so that it may be rinsed ofif. 

All the largely used chemicals are obtainable of good quality, 
as a rule, but in important investigations tests for purity and 
strength should be applied. The following notes will assist in this. 

Alcohol. — Ethyl alcohol, commonly called "grain alcohol," 
contains in its strongest commercial form about 95 per cent, 
of ethyl hydroxid, notable quantities of esters, aldehydes, 
fusel oil, and traces of acid. For some purposes — e. g., making 
standard solutions of alkali — it must be purified by redistilla- 
tion over sodium hydroxid. The absolute alcohol sold by 
dealers usually contains some water. The presence of water 
in alcohol may be detected by the evolution of acetylene when 
a little calcium carbid is added. This may also be used for 
removing small amounts of water, the liquid being redistilled, 
but hydrogen sulfid, hydrogen phosphid, and ammonium 
compounds may be introduced. Anhydrous copper sulfate 
is turned blue by alcohol containing water. 

Methyl alcohol. Crude wood-alcohol is of limited use in 
laboratory work. It contains much acetone. A purified 
article is now furnished, under the trade name '^ Columbian 
Spirit," which is about 98 per cent, methyl hydroxid and is 
free from notable amounts of impurities. It may be used 
with economy as a substitute for ethyl alcohol in many cases. 
It is more volatile, but traces of strong-smelling foreign matters 
may cause the odor to persist longer than with refined alcohol. 

Ether. Commercial ether contains notable amounts of al- 
cohol and water, but much purer samples can be obtained from 
dealers in laboratory supplies. To obtain good results with 
ether it is essential that it be as nearly as possible free from 
alcohol and water. The method of purification recommended 
by the A. O. A. C. is as follows: 

Commercial ether is washed with two or three successive 
portions of distilled water and solid sodium hydroxid added 



APPARATUS AND CHEMICALS 55 

until most of the water has been extracted. Carefully-cleaned 
metallic sodium, cut into small pieces, is added until there is no 
further evolution of hydrogen. The ether thus dehydrated 
must be kept over metallic sodium, and should be only lightly 
stoppered in order to allow hydrogen to escape. 

Chloroform, benzene, petroleum spirit and carbon tetrachlorid 
are usually obtainable of good quality. All are liable to contain 
water. This may be removed by shaking with anhydrous 
calcium sulfate or anhydrous copper sulfate and redistillation. 
Commercial chloroform is liable to decomposition, by which 
it becomes acrid. All volatile solvents are liable to contain 
appreciable amounts of non-volatile materials, and should be 
tested by evaporating a measured amount and weighing the 
residue. If this is appreciable the solvent should be distilled. 
Carbon tetrachlorid is well adapted for fat extraction when an 
open flame is used. Light petroleum, commonly known as 
benzin and gasolin, and often by other trade-names, should be 
purified by redistillation, selecting the portions which distil over 
below 50°. 

Sodium hydroxid. Several brands sold for household use 
are suitable for ordinary purposes, such as making standard 
alkali or in the Kjeldahl- Gunning process. 

Potassium hydroxid. The specially purified grades should 
be used. 

Sand and asbestos intended for moisture and extract deter- 
mination must be selected with care, and dried thoroughly 
before weighing. Common sand contains much material other 
than quartz ; asbestos fiber is often of inferior quality. 

Indicators. — Numerous indicators have been proposed, but 
for ordinary laboratory work litmus, phenolphthalein, and 
methyl-orange are usually preferred. 

Litmus. Litmus solution is now little used, but azolitmin, a 
pure blue color obtained from it, is a sensitive indicator. It is 
freely soluble in water but insoluble in alcohol. The solution 



56 FOOD ANALYSIS 

must ])c kept in an open bottle. Intermediate litmus-paper, 
which is convenient for ascertaining the reaction of liquids, is 
prepared as follows : A clear, fresh solution of litmus is divided 
into two equal portions; one of these is rendered purjjle-red 
(not bright red) by the cautious addition of dilute nitric acid; 
the other portion is then added and strips of good filter-paper 
soaked in the liquid and dried quickly. This paper will be 
affected by ordinary acid or alkaline solutions. It should be 
kept in the dark, protected from dust. 

Phenol phthalein. A solution of i gram in 100 c.c. of good 
(methyl or ethyl) alcohol is sufficient and keeps well. 

Methyl- orange. A solution of o.i gram in 100 c. c. water 
will be satisfactory. In titrating with methyl-orange very little 
of the indicator should be used. 

Cochineal. Many prefer this indicator for titrating am- 
monium hydroxid. 3 grams of pow^dered cochineal are macer- 
ated for several days, with occasional shaking, in 100 c.c. alcohol 
of about 20 per cent., and the solution filtered. 

Starch Indicator. — This is much used in titrations with 
iodin. As it spoils quickly, it is usually made as needed. 
Moerk has found that oil of cassia acts as a preservative without 
interfering with the efhcicAcy of the solution. 5 grams of 
good starch (preferably arrow- root) are mixed with about 100 
c.c. of cold water, and the mixture poured into 500 c.c. of boil- 
ing water with active stirring. The liquid is allowed to cool, 
2 c.c. of oil of cassia added, made up to 1000 c.c, shaken and 
preserved in a well-stoppered bottle. 

Standard acid. — The strength of dilute sulfuric acicj can be 
accurately determined by adding to a carefully measured 
quantity a slight excess of pure ammonium hydroxid, evapora- 
ting in a platinum basin to dryness and weighing the ammonium 
sulfate. The solution to be valued must contain nothing but 
sulfuric acid and w^ater, and the ammonium hydroxid must be 
entirely volatilized b}^ evaporation on the water-bath. 



APPLIED ANALYSIS 
GENERAL METHODS 

POISONOUS METALS 

The elements included under this title are mercury, arsenic, 
lead, tin, copper, zinc and chromium. Some very poisonous 
elements not likely to be encountered in foods, are not con- 
sidered in this connection: 

A. H. Allen has devised a general process for the detection 
of poisonous metals. A convenient quantity of the substance, 
say 25 grams, is mixed by degrees with sufficient strong sulfuric 
acid to moisten the mass thoroughly without making it fluid. 
About 2 c.c. will generally be required. Liquid material should 
be evaporated to dryness or nearly so at a low temperature 
before being treated with the acid. The mass is heated for a 
short time on the water-bath, after which the temperature is 
gradually raised to a point just below that required to volatilize 
the sulfuric acid, and maintained until the action seems to be 
complete. It is not necessary to carry on this part of the process 
until all the carbon is burnt off. The mass is allowed to cool, 
about I c.c. of strong nitric acid added, and the heating con- 
tinued until red fumes are evolved. Allen recommends the use 
of a porcelain crucible in these operations, but the Kjeldahl 
digestion flasks of Jena glass would probably serve, y Recently 
ignited magnesia, in the proportion of 0.5 gram for each cubic 
centimeter of the acid used, is incorporated with the mass and 
the mixture burned off at a dull red heat, preferably in a muffle. 
After cooling, the ash is moistened with nitric acid, again 
burned off, and the process repeated,, until all the carbon is con- 

57 



58 



FOOD ANALYSIS 



sumcd. The residue is treated with 0.5 ex. of sulfuric acid, 
heated until fumes are evolved, cooled, boiled with water, 
diluted without filtration to about 100 c.c, saturated with 
hydrogen sulfid, the solution fiUcrcd and examined according 



to tile following scheme: 



Aqukuus Solution may cont; 


tin zinc and iron. 


Precipitate and Residue may 


contain lead 


Add bromin water to destroy hydrogen sulfid. 


sulfid, stannic oxid, copper sulfid, or calcium 


convert iron into the ferric 


slate, l)oil, then 


sulfate. Fuse in ijorcelain crucible for lo 


add excess of ammonium 


hydroxid, boil 


minutes with 2 grams of mixed ix)tassium 


again, and filter. 




and sodium carbonates and i gram of sulfur. 
When cool, boil with water and filter. 


Precipi- 


Filtrate if blue 


, contains nickel. 


Residue. Boil with strong hy- 


Filtrate. 


tate may 


Divide into two portions: 


drochloric acid as long as hy- 


Acidulate 


contain 




i 


drogen sulfid is evolved, add 


with ace- 


iron (and 






a few drops of bromin water 


tic acid. 


p h s - 






to complete the oxidation of 


A yellow 


phates). 




1 


the copp)er sulfid, and filter if 
necessary. To the filtrate add 
excess of ammonium hydroxid, 
when a blue coloration will be 
indicative of copper. Acidu- 
late the liquid with acetic acid 
and divide into two fjortions: 


precip- 
itate of 
stannic 
sulfid in- 
dicates 
tin.^ 




I. Heat to boil- 


II. If zinc 


I. Add potas- 


II. Add potas- 






ing and add 


found in I, 


sium chro- 


s i u m fcrro- 






potassium 


for its deter- 


mate. A yel- 


c y a n i d J. A 






ferrocyanid. 


mination. 


low precipi- 


brownish 






White pre- 


acidulate 


tate indicates 


precipitate 






c i p i t a t e or 


the ammoni- 


lead. 


or coloration 






turbidity in- 


acal solution 




indicates co/»- 






dicates zinc. 


strongly with 
acetic acid, 
filter, if nec- 
essary, and 
precipitate 
the zinc from 
the filtrate by 
hydrogen sul- 
f i d . Any 
nickel pres- 
ent will also 
b e precipi- 
tated. 


I 


Pcr. 





Allen's scheme does not include chromium, which may be 
present as a constituent of lead chromate and will be found 
almost entirely in the precipitate and residue insoluble in 
water. For its detection a portion of this or of the original 
ash should be fused with sodium carbonate and potassium 
chlorate; the yellow melt, containing chromate, is dissolved in 



POISONOUS METALS 59 

the smallest possible quantity of water and slightly acidulated 
with hydrochloric acid. The liquid is then added to a test- 
tube containing a small amount of hydrogen dioxid overlaid 
with a little ether. In the presence of a chromate the water 
will acquire a blue color, which on sHght shaking will pass 
into the ethereal layer. 

When tin is known to be present, the amount may be found 
by treating the precipitate of stannic sulfid with strong nitric 
acid, igniting the metastannic acid formed, and weighing the 
resultant stannic oxid. For the detection of tin it is recom- 
mended to treat the stannic sulfid with hydrochloric acid and 
bromin water and boil the filtered liquid with iron wire to 
reduce to the stannous condition. The liquid is diluted and 
decanted from the undissolved iron and any precipitated 
material, and the tin detected by adding a drop of mercuric 
chlorid solution, which will produce a white or gray turbidity 
according to the amount of tin present. 

Copper may be estimated colorimetrically by means of 
ammonium hydroxid or potassium ferrocyanid. According 
to Bodmer & Moor, for very small amounts the ferrocyanid 
method is more accurate. Paul & Cownley determine copper 
as follows: The sample is carbonized in a platinum dish and 
extracted with a little hydrochloric acid; the insoluble residue 
is ignited with a little nitric acid, hydrochloric acid added, and 
the resulting mixture added to the original extract. The 
solution is then concentrated to about 30 c.c, placed in a 
weighed platinum dish, and the copper deposited with pure zinc. 
If the deposit is not of true copper color, it is dissolved in a little 
nitric acid and the copper determined colorimetrically. 

Zinc. — Evaporated fruits are liable to derive zinc from the 
trays on which the drying is conducted. Wiley gives the follow- 
ing process for determination : The sample is placed in a large 
platinum dish and heated slowly until dry and in incipient com- 
bustion. The flame is removed and the combustion allowed to 



6o FOOD ANALYSIS 

proceed, the lamp being applied from time to time, in case the 
burning ceases. The mass, when burned out, consists of ash 
and char. It is ground to line powder and extracted with 
hydrochloric or nitric acid, the residual char is burned to 
whiteness at a low temperature, the ash extracted with acid, 
the soluble portion added to the first extract, and the whole 
filtered. A drop of methyl orange solution is placed in the 
liquid and ammonium hydroxid added until it is only faintly 
acid. The iron is precipitated as ferric oxyacetate by adding 
50 c.c. of a solution of ammonium acetate, 250 grams to the liter, 
and raising the temperature to about 80°. The precipitate is 
separated by filtration, washed in water at 80° until free from 
chlorid, the filtrate saturated with hydrogen sulfid, allowed to 
stand until the zinc sulfid settles, and poured on a close filter. 
It is often necessary to return the filtrate several times before it 
becomes limpid. The collected precipitate is washed with a 
saturated solution of hydrogen sulfid containing a little acetic 
acid. The precipitate and filter are transferred to a crucible, 
dried, ignited, and the oxid weighed. 

Arsenic, if present in notable amount, may be detected by 
ReinscWs test, a liberal amount of hydrochloric acid being used, 
since arsenates do not otherwise respond to the test. Some 
water strongly acidulated with hydrochloric acid is placed in a 
test-tube, about half a square centimeter of bright copper foil 
added, and the liquid boiled gently for a few minutes. If the 
copper remains bright, showing that the reagents contain no 
arsenic, the material to be tested is added and the liquid again 
boiled for several minutes. If arsenic be present, a steel-gray 
stain will appear on the copper. The slip is removed, washed 
with distilled water, dried by pressure between filter-paper, 
placed at the closed end of a narrow glass which has been 
previously dried by heating nearly to redness. The tube is 
gently heated at the point at which the copper rests. The 
arsenic will be converted into arsenous oxid, which will collect on 
the cooler portions of the tube in octahedral crystals. 



POISONOUS METALS 6 1 

Reinsch's test cannot be applied in the presence of active 
oxidizing agents, such as chromates, chlorates, or nitrates. 

GutzeWs test, which is more delicate, is as follows: Place 
in a tall test-tube about a gram of pure zinc, 5 c.c. of diluted 
sulfuric acid (6 per cent.), and i c.c. of the sample. The 
mouth of the test-tube is covered with a tightly-fitting cap of 
three thicknesses of filter-paper. A drop of strong solution 
of silver nitrate is placed on the upper paper and the tube 
allowed to stand for 10 minutes in the dark. If arsenic be 
present, a bright yellow stain will appear on the filter-paper^ 
which, on the addition of water, becomes black or brown. A 
blank test should aways be made to establish the purity of 
the reagents. Sulfids (which may be detected by substituting 
lead acetate for the silver nitrate in the above test) must be 
oxidized to sulfates before applying the test. 

The test is delicate. A less rigorous one may be made by 
substituting a drop of a saturated solution of mercuric chlorid 
for the silver nitrate. If no yellow coloration appears after 10 
minutes, the sample may be considered free from arsenic. 

The purity of the reagents must be carefully ascertained 
before applying any of these methods. 

For the detection of minute amounts of arsenic, Marsh's test 
is used. The details as given by Haywood are generally 
applicable. 

The apparatus consists of a flask holding about 100 c.c, with 
a rubber stopper through which passes a long-stemmed separa- 
tory funnel — the tube of which should reach nearly to the 
bottom of the flask — and an exit tube bent at a right angle. 
The flask should stand in a basin containing cold water. The 
exit connects with a bulb-tube containing a small amount 
of lead acetate solution, to absorb sulfur, selenium, and tel- 
lurium. To this is connected a calcium chlorid tube, and, 
finally, a tube of very resistant glass, about 20 cm. long and not 
over 0.5 cm. caliber. It must be drawn out to nearly capillary 



62 



FOOD ANALYSIS 



narrowness about the middle. A piece of fine wire-gauze is 
wrapped around the tube for a few centimeters on the wide part 
nearer the flask. The gauze must not reach to within a centi- 
meter of the narrow part. Two Bunsen burners must be ar- 
ranged so as to be used at once to heat the gauze. The general 
arrangement is as figure 2>37 except that the protecting gauze, 
extra burner and stem of the separator are not shown. 
The burners are placed so that the flames meet and the gauze 
is at that point. The bulb-tube may be placed in water. The 
extra-tube, closed by a pinch-cock, is convenient but not neces- 
sary. If used, care should be taken that the pinch-cock closes 
it well. 




Fig. S3. 



For use, three grams of arsenic-free zinc arc placed in the 
flask and then 30 c.c. of dilute pure sulfuric acid (i to 8). The 
apparatus is connected and the hydrogen allowed to flow for 
15 minutes, after which the gauze is heated strongly for 20 
minutes. No deposit should appear in the tube. 

The prepared material (see below) is placed in the funnel and 
gradually run into the flask. The action is continued for 
about an hour, the portion of tube within the gauze being kept 



POISONOUS METALS 63 

very hot all the time. The tube is allowed to cool and the 
extent and appearance of the deposit compared with tubes of 
known value. 

The sample is best prepared by mixing a small weighed 
portion in a porcelain basin with from i to 5 c.c. of a mixture of 
nitric and sulfuric acids. The mass is heated with a low flame 
until it has granulated and fumes of sulfuric acid are not abun- 
dant. The charred mass is broken up, mixed with a little 
water, and boiled to get rid of sulfurous acid. It is filtered, the 
residue washed, and the filtrate and washings made up to a 
definite volume (about 40 c.c). It is then ready for the de- 
termination. 

The comparison tubes are made by using measured volumes 
of a standard solution of arsenous oxid in such amount as will 
contain the following fractions of a milligram of elementary 
arsenic, operating with each solution as directed above: 0.005; 
o.oi; 0.02; 0.03; 0.04; 0.05; 0.06; 0.07. These deposits 
(mirrors) should be sealed and kept in the dark. Even then 
they fade, and for accurate observation should not be over three 
weeks old. 

• The standard solution is made by dissolving 0.0132 gram of dry 
pure arsenous oxid and o.i gram pure sodium acid carbonate, 
in 100 c.c. of water. The mixture is kept hot until the arsenous 
oxid is dissolved, cooled, slightly acidified with sulfuric acid, 
and made up to 1000 c.c. Each c.c. of this solution contains 
o.ooooi gram of elementary arsenic. Aliquot portions are used 
for making the standard mirrors. 

As this test is extremely delicate, great care must be taken to 
ensure purity of all reagents. It must be borne in mind that 
most natural substances will give slight reactions for arsenic 
by it. 

All junctions must be as tight as possible. The connected 
points of the different pieces should be of the same diameter and 
the junctions made by short, close-fitting, pure rubber tubing. 



64 FOOD ANALYSIS 

Great care must be taken that the apparatus is thoroughly 
cleaned between each use. In cases in which the results are to 
be used in criminal prosecutions the apparatus should be new. 



COLORS 

At present, the colors used in food-articles are mostly synthetic 
products, commonly called "anilins," but largely derived from 
other coal-tar materials. 

Natural organic colors — annatto, cochineal, turmeric, indigo, 
saffron, and chlorophyl — are used to a limited extent, but 
mineral colors are rarely employed. Ferric oxid is used in 
some chocolate substitutes. 

The identification of individual colors in mixture with foods 
or beverages is difficult, often impossible, with methods at 
present available. It is possible in many cases to distinguish 
between artificial and natural colors. The following method is 
generally applicable for distinction between these classes. 

Pure white wool (the material known as "nun's veiling" 
is satisfactory) is cleaned by boiling for a short time in soap- 
suds, washed thoroughly with water, well-dried, and cut into 
slips about 3 X lo cm. They should be kept in a closed bottle. 

A convenient quantity of the material, depending on the 
amount of color, is placed in a beaker. For ordinar}' liquids, 
100 c.c. will suffice; for soHds and semi-solids from 5 to 25 
grams. In the latter case, water should be added to make the 
bulk about 100 c.c. The beaker is placed in a water bath, i c.c. 
of hydrochloric acid added and a slip of the cleaned wool. The 
liquid is kept in the boiling water for a moderate time. If not 
appreciably dyed in fifteen minutes it may be assumed that no 
coal-tar color is present. In most cases, however, some color 
will be imparted, even if only natural colors are present. The 
shp is washed well with cold water, warmed for a few minutes 
in very dilute hydrochloric acid, again washed well, and im- 



COLORS 65 

mersed in about 25 c.c. of water to which 2 c.c. of strong 
ammonium hydroxid have been added. By this means, the 
color will generally be dissolved promptly from the slip, but it 
may be necessary to allow much longer action. When the cloth 
is nearly or quite decolorised, it is taken out of the liquid. The 
latter is diluted to about 50 c.c, rendered moderately acid by ad- 
dition of hydrochloric acid, another slip of cleaned wool im- 
mersed and the liquid heated in the water bath. Coal-tar 
colors and some lichen colors (archil, cudbear, litmus) will give 
marked second dyeing. 

Lichen colors, including a sulfonated orcein, now often 
used in food articles, are distinguished by Tolman's method,^ 
depending on the fact that amyl alcohol removes them from 
the ammonium hydroxid solution. If, therefore, a double dye - 
ing is obtained, the process should be repeated, but the am- 
monium hydroxid solution should not be acidified but shaken 
with pure amyl alcohol. If this acquires a purplish red tint, it 
is evaporated on the steam bath, the residue dissolved in water 
and the solution mixed with a little tin and hydrochloric acid. 
Lichen dyes are bleached by this method and are restored by 
ferric chlorid. These reactions exclude all azo-dyes and ma- 
genta. 

Some tests adapted specially to the recognition of colors in 
particular foods will be described in connection with such foods. 

When dyes intended for food-coloring are to be examined 
in bulk, the following methods are advantageous : 

A small quantity of the sample (o.i to 0.25 gram) is heated 
on platinum foil. Nitro-colors show more or less deflagra- 
tion at first. Sulfonated colors form a fusible residue, in 
which the carbon burns with difficulty. It will be advanta- 
geous to add some oxidizing agent (potassium nitrate, potas- 
sium chlorate, or sodium nitrate). It is not necessary to 
burn off all the carbon. The mass is allowed to cool, boiled 
up with water acidulated with hydrochloric acid (this may 
7 



66 FOOD ANALYSIS 

cause the evolution of a little hydrogen sulfid), and barium 
chlorid added. A copious white precipitate will occur if the 
color is a sulfonated one. 

For detection of arsenic the Reinsch test may be applied or 
llu' color may l)c examined for all the important poisonous 
metals by the scheme given on page 58. 

Identification of colors may sometimes be accomplished by 
routine methods, several of which are given in the following 
pages. The first is Green's adaptation of Weingartner's tables. 
It is reproduced without modification of spelhng or nomenclature 
from Allen's ''Commercial Organic Analysis," edited by 
Matthews. The reagents required are as follows: 

Tannin solution. Tannin, i gram; sodium acetate, i gram; 
water, 10 c.c. 

Zinc dust. 

Dilute hydrochloric acid: Hydrochloric acid, 5 c.c; water, 
15 c.c. 

Ammonium hydroxid solution. 

Chromic acid solutioji: Chromium teroxid, i gram; water, 
100 c.c. 

Chromic-suljuric acid solution: Chromium teroxid, i gram; 
strong sulfuric acid, 2.5 c.c..' water, 100 c.c. 

Strong sodium hydroxid solution: Sodium hydroxid, 33 
grams; water, 67 c.c. 

Dilute sodium hydroxid solution: Sodium hydroxid, 5 grams; 
water, 95 c.c. 

Alcohol. 70 per cent. 

In applying the scheme a primary division is made into 
dyes soluble and insoluble in water. The former are divided 
by means of the tannin solution into the so-called basic and 
acid groups. The dyes which in aqueous solution are pre- 
cipitated by tannin solution are termed basic dyes. 

The reduction with zinc dust is best made by adding a little 
of the zinc dust to the hot dyestuflf solution contained in a 



COLORS 67 

test-tube, agitating, and adding dilute hydrochloric acid drop 
by drop until decolorized. Excess of acid should be care- 
fully avoided. When the color acid is quite insoluble, the 
reduction is made with zinc dust and ammonium hydroxid. 
The reduced solution is decanted upon a small filter; if the 
color does not return in a few minutes, the paper is moistened 
with chromic acid solution. In the case of acid colors the 
chromic-sulfuric acid solution should be used. As some dyes 
do not show their color in presence of free acids, the paper 
should be exposed to the fumes of strong ammonium hydroxid 
solution before deciding as to whether the color will return. 



68 



FOOD ANALYSIS 



Si 






cq 



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"t^ <-t 



- ~ aj 

•r- J. <_> 

<D t 3 



c . 
> is 












3 
cy^ 

C . 

o 2 ^ 

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2 t-i 2 

C OJ-^; 
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if 5^ 

a.3 a 

gvOg 

O cS <^ 

0) 
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tf 



o-r: c 3 



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:<cposure to air: 
Int Colors. 










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t-. 3*-,— . -— - - s ci'7;K~- — 


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COLORS 



69 



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70 



FOOD ANALYSIS 



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COLORS 71 

rota's scheme for recognition of colors^ 

Two special reagents are used. 

Stannous chlorid 10 per cent, solution in hydrochloric acid. 

Potassium hydroxid 20 per cent, solution in water. 

The material may be tested in solution in water or alcohol. 
It should be diluted with water or alcohol, as required, until the 
color is not deep. Turbid liquids must be filtered. A com- 
parison test of the solution should be made with hydrochloric 
acid alone, as many effects of the stannous chlorid reagent are 
due to the acid and not to the tin compound. Some colors 
require considerable time to effect a change. 

To a portion of the solution a small amount of stannous chlorid reagent 
is added, the mixture shaken and heated to boiling. The same test is applied 
to another portion, using hydrochloric acid alone. 

1 . The stannous chlorid decolorizes the liquid (see A) . 

2. The color is not affected more than by hydrochloric acid alone (see B). 

A. The liquid is mixed with either ferric chlorid or hydrogen dioxid 

or is shaken with air. 

The color does not return. Nitro-, nitroso-, azo- and hy- 

drazo-colors. Picric acid, 
naphthol yellow. Ponceau, 
Bordeaux, Congo-red. 

The color is restored. Indogenid, imido-quinones» 

methylene blue, safranin, 
indigo-carmine. 

B . A part of the original solution is mixed with some of the potassium 

hydroxid and warmed. 

The liquid is decolorized Amido-derivatives of di- and 

or rendered turbid. triphenylmethane, auramins, 

, acridins, quinolins and colois 

from thiobenzirttl. 
The reagent produces no 
discoloration or turbid- 
ity. Monamid, diphenylmethane, 

oxyketone, eosins, aurin, aliz- 
arin and most natural colors. 

Many of the powders and pastes sold for imitating natural 
vegetable colors are mixtures of several coal-tar colors often 



72 FOOD ANALYSIS 

representing several t}'p)es, so that the above schemes will give 
confusing results. The identification of the ingredients of such 
mixtures can generally be done only by expert color-chemists, 
but some information may be obtained by dyeing successive por- 
tions of wool in the same bath. The color with the strongest 
attraction is taken out in greater amount in the first dyeing, and 
a series of dyed slips will be obtained shoeing the principal 
tints of the mixture. Information is also often srained bv dve- 
ins: in difi"erent baths. The color material to be tested is made 
up ^"ith about loo c.c. of water, a few grams of sodium sulfate 
and 2 c.c. of strong sulfuric acid. Another bath is made with 
a few grams of alum in loo c.c. of water. A separate piece of 
wool is dyed in each bath. If more than one color is pres- 
ent a notable difference in the dyeing may be obtained. 

The following process for cochineal is due toGirard & Dupre:* 
The material is dissolved in water if not already in solution, 
moderately acidulated with hydrochloric acid, and shaken out 
with amyl alcohol. If cochineal is present, the alcohol will be 
colored. It is separated, washed with water until neutral and 
diWded into two portions. To one, a dilute solution of uranium 
acetate is added. Cochineal produces a characteristic emerald 
green. To the other portion is added a little ammonium hy- 
droxid. Cochineal gives a violet solution, but this reaction is 
not characteristic, as it is given by many fruit colors. See also 
pages 65 and 74, and the detection of carmine in meat, under 
''Flesh Foods." 



COLORS 73 

For the detection of colors used in egg substitutes, Winton & 
Bailey give a special scheme:^ 

The material is treated with 95 per cent, alcohol. 

A. The color dissolves. 

1. Filter-paper is dipped in the solution, dried, moistened with a 

mixture of hydrochloric and boric acids and again dried. 
h. The color becomes cherry -red, changed to grayish-blue on 
addition of ammonium hydroxid. Turmeric. 

2. The color is not affected by these reagents. 

a. The alcoholic solution on evaporation leaves a deposit soluble 
in water; the solution is partly decolorized by hydrochloric 
acid. Nitro-colors. 

h. The deposit from alcohol is soluble in water. True egg color. 

B. The yellow color is not soluble in the alcohol. 

I. The material is treated with a inixture of 90 per cent, of alcohol 
and 10 per cent, hydrochloric acid. 
It dissolves with an orange color. Filter-paper dipped in this 
and dried becomes rose-red on drying at room-tempera- 
ture. Azo-colors. 

The annexed synopsis of reactions of natural colors with some 
common color-reagents is from results obtained by LaWall from 
authentic samples. The ammonium hydroxid, hydrochloric 
acid and stannous chlorid are the ordinary laboratory solutions, 
added in small amounts to water-solutions of the color. The 
other reagents are : 

1. Double dyeing as described on page 64. The figures refer to the order 
of the dyeing. "Amm" following abbreviation of a color-name, means the 
effect produced by ammonium hydroxid on the first dyeing. As a rule, second 
dyeing gave no noteworthy effect. 

2. Good kaolin was shaken with a portion of the solution and the liquid 
filtered. 

3. A piece of zinc was dropped into the hydrochloric acid solution of the 
color. 



74 



FOOD ANALYSIS 



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76 FOOD ANALYSIS 

PRESERVATIVES 

The decomiJosilion of food is prevented by sterilization or 
by addition of preservatives. Some preservatives — e. g., com- 
mon salt, niter, acetic acid, and wood smoke — have been known 
from early times and are still in vogue. Among the • more 
important of the newer forms are salicylic acid, benzoic acid, 
sodium benzoate, beta-naphthol, saccharin, abrastol, formal- 
dehyde, fluorids, silicofluorids, sulfites, boric acid, and borax. 
Others, mostly synthetic coal-tar derivatives, have been sug- 
gested and, to a limited extent, used. Most acids are antiseptic. 

Each of the substances above named has special adap- 
tabilities; some of them are widely applicable, and hence are 
largely used. The permissible food-preservatives are not 
distinctly germicidal and must remain in the food if continued 
preservation is desired. 

Salicylic acid is a white crystalline powder, soluble in 500 
parts of cold water, more freely in alcohol. Ether, petroleum 
spirit, chloroform and carbon tetrachlorid dissolve it readily 
and remove it from an acidified water-solution. It distils in a 
current of steam. Its most characteristic reaction is the violet 
produced by ferric salts. 

Salicylates exist normally in many vegetable substances; in 
a few in considerable amount, in many, such as common edible 
berries, in very small amounts, but still recognizable by delicate 
tests. Care must be taken therefore in interpreting the results 
of such tests. 

Sodium benzoate is usually sold as a granular white powder 
which has a slight aromatic odor and a nauseous taste. It is 
freely soluble in water. In the United States it is the usual 
preservative for catsups, jams, jellies, mince-meat, and pre- 
serves. 

Benzoic acid is not frequently used in food articles, but some 
of it may be formed from sodium benzoate by the action of acids 
or acid salts in the food. 



PRESERVATIVES 77 

Saccharin. Commercial saccharin is somewhat variable in 
composition. It is a white, crystalline, intensely sweet powder, 
soluble in looo parts of cold and loo parts of boiling water. 
It is more soluble in alcohol, glycerol, and ether, and very 
slightly soluble in chloroform, benzene, and petroleum spirit. 
Ether removes it from its aqueous solutions. Pure saccharin 
is slightly volatile at ioo° and leaves no ash, but impurities may 
be present in the form of sodium salts, and considerable ash, 
principally sodium sulfate, may be left upon ignition. 

fd-naphthol is a white crystalline powder, slightly soluble in 
water, freely in alcohol, ether, chloroform, benzene, fats, and 
alkaline solutions. It is wholly volatile on ignition. It is 
liable to contain small amounts of a-naphthol. The so-called 
hydronaphthol is substantially the same as /9-naphthol. 

Abrastol or asaprol (calcium /?-naphthol-a-monosulfonate) 
is a colorless or light reddish powder freely soluble in water and 
alcohol. In dilute solution in water it produces with a solution 
containing mercuric nitrate and nitric acid, a canary-yellow 
liquid. Stronger solutions produce a yellow precipitate. 

Formaldehyde is a gas freely soluble in water, from which 
solution a polymeric modification is easily obtained as a white 
solid, volatilized only at a temperature above the boiling- 
point of water. Formaldehyde is principally sold as a 40 per 
cent, watery solution designated by the copyrighted name 
"formalin." More dilute solutions are sold under a variety 
of fanciful and misleading names. The 40 per cent, solution 
is a colorless liquid with a slight, somewhat acrid odor and 
a faint acid reaction, the last property being probably due to 
small amounts of formic or acetic acid produced by oxida- 
tion. When this solution is boiled, most of the formaldehyde 
distils readily with the steam; but if the fresh distillate be 
evaporated at a lower temperature, — as, for example, on a 
shallow dish placed over boiling water, — a large part is con- 
verted into the solid form. All the modifications of formaldc- 



78 FOOD ANALYSIS 

hyde have active reducing qualities and exhibit strong tendency 
to combine with proteids so as to form insoluble bodies. In 
the preservation of food, the commercial formalin is almost ex- 
clusively used. 

Sulfites. The acid salts are more active than the neutral 
form and are more used. Calcium sulfite is also frequently 
employed. Sulfites are white solids freely soluble in water 
and glycerol, but not appreciably in alcohol, or the solvents 
immiscible with water. Their antiseptic action being strongly 
exerted upon yeast, they have been used largely to control or 
prevent alcoholic fermentation. The detection of sulfites 
being based upon the recognition of the sulfurous acid derived 
from them, a specific description of each will not be needed. 

Boric acid, Borax. A mixture of these is frequently sold 
under trade names, such as " Preservaline " and "Rex Magnus." 
They are also used separately. Both are white powders soluble 
in water; borax is practically insoluble in alcohol, boric acid 
freely soluble. Both are non- volatile at a red heat, but a watery 
solution of boric acid cannot be evaporated without considerable 
of the acid passing off with the steam. Borax has an alkaline 
reaction; boric acid is acid to litmus, but turns turmeric paper 
brown when its solution is evaporated on it. 

When boric acid is heated with glycerol, tritenyl borate is 
produced as a thick sirup miscible in all proportions with cold 
water and decomposed by hot water. By evaporation it can 
be obtained in the form of a transparent, glassy, brittle mass 
which absorbs water readily. A preparation made by dissolv- 
ing borax in glycerol has also been offered as a preservative, 
but is little used. These glycerol preparations have been sold 
under various names, such as " boroglyceride " and ''glyceride 
of boric acid." 

Borates are present in appreciable amount in many fruit- 
juices. 

Fluorlds, borofluorids, and silicofluorids. The sodium, potas- 



PRESERVATIVES 79 

sium and ammonium compounds, have been principally used, 
being among the few forms soluble in water. They are white 
powders, not volatile at a red heat except ammonium fluorid. 
The last has been sold under the name "antisepticum." 

Detection of Preservatives. — Owing to the difference in 
the chemical character of preservatives and of the food articles 
in which they are used, few general methods can be given; the 
examination must be conducted with reference to the material 
likely to be present. The following are suggestions in this 
direction : In meats, boric acid and sulfites ; in milk and milk 
products, formaldehyde and boric acid, occasionally salicylic 
acid. In jams, jellies, mince-meat, and table delicacies, benzoic 
and salicylic acids or their salts; occasionally boric acid. In 
cider and some other fruit juices, salicylic acid and sulfites. In 
fermented beverages and malt extracts, salicylic acid, sulfites, 
fluorids, silicofluorids, borofluorids ; abrastol may be employed, 
but the data in regard to it are limited. Saccharin is likely to 
be present in beers, wines, and sweetened articles. 

Several preservatives are easily extracted from food articles by 
shaking with ether which dissolves them. The solution should 
be slightly acid. If not, a little sulfuric acid should be added. 
If the extraction be repeated with several portions of the solvent 
an approximate quantitative determination may be made. The 
shaking must be vigorous, so as to bring the solvent in contact 
with all parts of the sample. In many cases this will produce an 
emulsion which separates very slowly. The application of the 
centrifugal method will be useful in this case. The addition of 
more of the solvent and the cooling of the material is also 
advised. 

The following descriptions are adapted especially to the 
conditions under which the different preservatives are likely 
to be found. As they are somewhat soluble in water, solid 
or semi-solid materials may be exhausted with water and the 
liquid concentrated at a low temperature. In many cases the 



8o FOOD ANALYSIS 

sample may be strained through muslin and the tests applied to 
the filtrate. 

The volatility of some preservatives, especially in a current 
of steam, is occasionallv serviceable. Formaldehvde mav be 
thus obtained from milk. Benzoic acid, saccharin and sulfites 
may be separated by mixing about 200 grams of the sample with 
5 c.c. of a 20 per cent, solution of phosphoric acid, and distilling 
nearly to dryness. Benzoic and sulfurous acids distil, and the 
saccharin remains in the flask. Sulfuric acid may also be used. 
A current of steam through the distilHng flask is more efficient. 

Salicylic acid. This is usually detected by extraction with 
an immiscible solvent. 25 to 50 c.c. of the sample are rendered 
feebly acid with a few drops of sulfuric acid and shaken vigor- 
ously with about an equal bulk of a mixture of equal parts of 
ether and petroleum spirit, the liquids are allowed to separate, 
as much as possible of the solvent is drawn off, filtered, .and 
evaporated at a gentle heat. When salicylic acid has been 
added as a preservative, distinct needle-like crystals will be 
usually seen. A few drops of water should be added and then 
a drop of very dilute ferric chlorid solution. The reaction of 
salicylic acid is distinct. When a crystalline deposit cannot be 
obtained, a larger quantity of the sample may be concentrated 
at a gentle heat and extracted as above. (See under ''Alcoholic 
Beverages.") 

Some analysts prefer chloroform as the extracting liquid. 
In this case the shaking should be done in a stoppered sepa- 
rator, that the solvent may be readily drawn. A solution of 
ammonio-ferric alum is in some respects preferable to ferric 
chlorid as a testing agent. If 50 c.c. of the sample properly 
extracted does not give a visible deposit of the acid, it is not 
likely that it has been added as a preservative. 

Saccharin. A suitable amount of the sample (50 or 100 
c.c.) is acidified with dilute (25 per cent.) sulfuric acid and 
extracted with a mixture of equal parts of petroleum spirit 



PRESERVATIVES 8 1 

boiling below 6o°'*and ether. The solvent is evaporated at a 
gentle heat. The presence of saccharin in the residue may be 
detected by the taste. 2 c.c. of a saturated solution of sodium 
hydroxid are added and the dish heated until the residue dries 
and then to 210-215°, and maintained thus for half an hour. 
The saccharin is converted into salicylic acid, which may be 
detected in the residue by acidulating it with sulfuric acid and 
applying the ferric chlorid test. If salicylic acid be present 
originally in the sample, the residue from the petroleum spirit 
and ether solution is dissolved in 50 c.c. of dilute hydrochloric 
acid, bromin water added in excess, the liquid shaken well, 
and filtered. Salicylic acid is completely removed as a bromi- 
nated derivative. The filtrate is made strongly alkaline with 
sodium hydroxid, evaporated, and fused as described above. 

A substance capable of giving a reaction by this method often 
exists in wine. For the elimination of this error, see under 
"Alcoholic Beverages." 

Benzoic acid and henzoates. Mohler's method: About 
100 grams of the sample are made alkaline with sodium hydroxid 
and evaporated to a paste, which is then acidified with hydro- 
chloric acid, mixed with sand, and extracted with ether. The 
ether is evaporated spontaneously, the residue moistened with 
2 c.c. of sulfuric acid, heated until acid vapors escape (at about 
240°), and a few decigrams of sodium nitrate added in small 
portions, until the liquid becomes colorless. The liquid is 
poured into excess of ammonium hydroxid and a drop of 
ammonium sulfid solution added. Benzoic acid is indicated by 
a yellow, changing to reddish-brown. 

Peter's method: The material is made slightly acid and ex- 
tracted with chloroform, which is then evaporated sponta- 
neously. The vessel containing the residue is placed in melting 
ice, 2 c.c. of sulfuric acid added, and stirred until the residue 
is dissolved. Barium dioxid is dusted into the mass, with con- 
stant stirring, until the liquid begins to foam, when 3 c.c. of 



82 FOOD ANALYSIS 

hydrogen dioxid (3 per cent.) are added drop by drop. The 
dish is then removed from the cold bath, the contents diluted 
with water to convenient bulk, and filtered. The acid filtrate 
is extracted with chloroform. The benzoic acid will have been 
converted into salicylic acid by the process and the latter may be 
detected by dilute solution of ferric chlorid or ammonio-ferric 
sulfate. 

Boric acid and borax. These may be detected in many 
food-articles, especially milk and milk products, by the follow- 
ing test: A few drops of the sample or of a solution obtained 
by shaking some of it in water are mixed with a drop of strong 
hydrochloric acid and a drop of strong alcoholic solution of 
turmeric, evaporated to dryness at a gentle heat, and a drop 
of ammonium hydroxid added to the residue when cold. A 
dull green stain shows that boric acid is present. 

Borates being normal constituents of many fruits, quali- 
tative tests are not sufficient to determine if the preservative 
has been added. For methods of quantitative determination, 
see under "Alcoholic Beverages." 

Fluor ids. 100 grams of the sample are made slightly alka- 
line with ammonium carbonate, heated to boiling, a few centi- 
meters of calcium chlorid solution added, and heating con- 
tinued for 5 minutes. The precipitate is collected, washed, 
dried, transferred to a platinum crucible, and ignited. When 
the mass is cold, a few drops of strong sulfuric acid are added, 
and the crucible covered with a piece of glass partly protected 
on the lower side by paraffin. The bottom of the crucible is 
then heated for an hour at a temperature between 75° and 80°. 
The glass is etched if fluorids are present. 

Borofluorids and silico fluorids. 200 grams of the sample 
are made alkaline with calcium hydroxid solution, evaporated 
to dryness, incinerated, and the ash extracted with sufficient 
acetic acid to decompose carbonates. The residue is col- 
lected on a filter, washed, again extracted with acetic acid, 



PRESERVATIVES • 83 

and filtered. The filtrate contains any boric acid that may be 
present and is tested for this substance as directed on page 
82. The insoluble residue contains the calcium silicate and 
calcium fluroid. The filter and residue are ashed, a portion 
of the mass mixed with a little precipitated silica and 2 c.c. 
of sulfuric acid, and placed in a short test-tube to which is 
attached a small U-tube containing a few drops of water. 
The test-tube is heated cautiously in a water-bath; any sili- 
con fluorid that may be formed from fluorin present will pro- 
duce a gelatinous deposit in the U-tube. If boric acid has 
been found in the filtrate noted above, it may be assumed that 
any fluorin is in the form of borofluorid; but if boric acid is 
not present, the other portion of the ash from the filter and 
residue is treated with sulfuric acid without previous addition 
of silica. If gelatinous silicic acid be formed, the compound 
was originally silicofluorid. 

Formaldehyde. The tests for formaldehyde have been 
mostly adapted to its detection in milk. 

One of the most delicate and positive reactions of formalde- 
hyde is as follows: To a few c.c. of the suspected liquid, a 
pinch of phenylhydrazin hydrochlorid is added, the liquid 
shaken and a drop of a dilute solution of sodium nitroprussid 
added and then a few drops of sodium hydroxid. A deep blue 
color is at once produced with formaldehyde. The nitro- 
prussid solution should be fresh. The test is applicable to 
milk, but the color is grayish-green. 

Another test is the addition of a small amount of a solution of 
I per cent, of phloroglucol and about 25 per cent, of sodium 
hydroxid in water. This produces a rose-red. The test is best 
applied by running the test solution by means of a pipet under 
the suspected liquid. 

Formaldehyde may be obtained pure by distillation of the 
sample, especially in a current of steam. An investigation by 
Leonard, H. M. Smith, & Richmond showed that with or- 



84 FOOD ANALYSIS 

dinary aqueous solutions, about 30 per eent. of the formalde- 
hyde has passed over when 20 per cent, of the liquid has been 
distilled, and nearly 50 per cent, when 40 per cent, of the liquid 
has been distilled. A larger })roportion distils if sulfuric acid 
be added to the liquid. For details of this and for other tests 
for formaldehyde, see under "Milk." 

Determination oj Formaldehyde. B. H. Smith,'' who also in- 
vestigated the methods for this purpose, finds that the choice will 
depend on the strength of the solution. For moderately strong 
solutions the iodin method of Romijn is satisfactory. 

10 c.c. of the solution, which should be diluted so as not to 
contain more than 3 per cent of formaldehyde, are mixed with 
25 c.c. ^ iodin solution and sufficient strong sodium hydroxid 
solution added to make the liquid bright yellow. After stand- 
ing 10 minutes, hydrochloric acid is slowly added until a 
marked brown liquid is produced. The iodin is then titrated 
with thiosulfate in the usual way. The amount of iodin that 
has been taken up, multiplied by 0.118, will give the amount of 
formaldehyde. A blank experiment should be made and any 
necessary correction applied. 

For dilute solutions, the potassium cyanid method is best. 

30 c.c. of ~ silver nitrate solution are acidulated with 15 drops 
of nitric acid. 10 c.c. of this solution are mixed with 10 c.c. of 
normal potassium cyanid solution (6.5 grams in 1000 c.c), then 
water to make 50 c.c, the liquid shaken, filtered through a dry 
filter and 25 c.c. set apart for titration as below (Volhard's 
method). 

Another 10 c.c of cyanid solution are mixed wath a measured 
amount of the formaldehyde solution (which must not contain 
more than 0.03 gram of formaldehyde), the mixture added to 
another 10 c.c. of the acid silver nitrate solution, shaken, made 
up to 50 c.c, filtered and 25 c.c of the filtrate taken as before. 
The two solutions contain excess of silver, but the second con- 
tains more, because the formaldehyde converts the cyanid into 
a compound that does not precipitate silver. 



PRESERVATIVES 85 

Standard thiocyanate solution is prepared by dissolving lo 
grams of potassium thiocyanate (or 8 grams of ammonium 
thiocyanate) in water to make looo c.c. The solution is ap- 
proximately -^. Its value in silver must be determined thus : 

50 c.c. of -^ silver nitrate are mixed with i c.c. of nitric 
acid and i c.c. of saturated solution of ammonium ferric sul- 
fate, and thiocyanate solution added until a faint permanent 
brown is produced. 

The titration of the acid filtrates is conducted in the same 
manner. To each filtrate is added i c.c. of ferric sulfate and 
then the thiocyanate until the faint permanent brown is ob- 
tained. If the thiocyanate is exactly -^, the difference in c.c. 
required for the two filtrates multiplied by 0.006 will give the 
amount of formaldehyde in the quantity originally taken. 

If the thiocyanate is not ~^ the result must be reduced to that 
basis. 

For detection of sulfites see under "Alcoholic Beverages." 
13-naphthol. Several allied antiseptics of this type may be 
detected by the following method: 200 grams of the sample 
are acidified with sulfuric acid and distilled with open steam 
until 150 c.c. of distillate are obtained. This liquid is shaken 
with 20 c.c. of chloroform, the latter withdrawn, rendered 
alkaline with potassium hydroxid, and heated almost to boihng 
for a few minutes. Color changes as follows : 

Salol, light red. 

Phenol, light red, to brown, to colorless. 

/3-naphthol, deej) blue, to green, to brown. 

A portion of the distillate may also be tested as follows : 25 c.c. 
are made faintly alkaline with ammonium hydroxid, then 
faintly acid with nitric acid and then a drop of strong sodium 
nitrite solution. /9-naphthol develops a rose red, but the reaction 
is sometimes uncertain and seems to be affected by light. The 
so-called hydronaphthol gives the same effect. 



86 FOOD ANALYSIS 

Ahrastol {Asaprol). A characteristic reaction for abrastol is 
that described by Pintus'' ; the yellow produced by acid mercuric 
nitrate solution prepared as directed for the clarification of milk 
(see under Milk). 

It can be extracted from jellies, fruit juices, wines and similar 
articles by acidulation with dilute sulfuric acid and agitation 
with ether, petroleum spirit, chloroform or carbon tetrachlorid. 
On adding to the immiscible solvent a small amount of mercuric 
nitrate solution and shaking the liquids for a few seconds, the 
watery liquid will become yellow, rapidly changing to bright 
red.' ' 

The following method, de\'ised by Sinabaldi, especially for 
wine, is applicable to other food-articles. 

50 c.c. of the sample are made alkaline by cautious addition 
of ammonium hydroxid, shaken gently for two minutes with 
amyl alcohol, and the liquids allowed to separate. If this does 
not occur a Little common alcohol should be added. The amyl 
alcohol is decanted, filtered if turbid, and evaporated to dr}*ness. 
The residue is thoroughly mixed with a mixture of i c.c. of nitric 
acid and i c.c. of water, heated on the water-bath until half of 
the liquid is evaporated, transferred to a test-tube by the aid 
of I c.c. of water, 0.2 gram of ferrous sulfate added and then 
ammonium hydroxid to excess with constant shaking. If the 
resulting precipitate is reddish, it is dissolved in a few drops of 
sulfuric acid and treated with ferrous sulfate and ammonium 
hydroxid as before. As soon as a dark greenish precipitate 
has been obtained, it is dissolved in sulfuric acid, the liquid 
well shaken and filtered. In the absence of abrastol the filtrate 
is light yellow, with abrastol in appreciable amount it is red. 



SPECIAL METHODS 

STARCH 

Detection. 

The reaction with iodin affords a delicate method for detect- 
ing starch. The color is shown by undissolved granules, but 
it is more satisfactory to dissolve it by boiling with water, 
allowing the solution to cool and adding the iodin, preferably as 
potassium iodid-iodin solution (p. 26). If the proportion of 
starch be large, an almost black precipitate will be formed. 
The depth of color will be some indication of the amount 
present, but exact determinations cannot be made by this 
method. 

In the undissolved condition, starch may be recognized 
by the microscope and its source often determined. A magnify- 
ing power of from 150 to 300 diameters will be required. The 
characteristics of the granules are seen more vividly by mount- 
ing them in a dense medium such as chloral hydrate solution or 
glycerol (p. 26) and arranging the reflecting mirror so as to 
throw an oblique light upon the object. By this means distinct 
markings, termed hilum and concentric rings, are recognized. 
If the chloral-hydrate iodin solution (p. 26) be employed for 
mounting, or if a drop of the potassium iodid-iodin solution be 
introduced under the cover of a glycerol- or water-mounting, 
the granules will become blue. 

With polarized light, many starches show on the dark field — 
i. e., with crossed nicols — dark bands radiating from the hilum, 
giving the appearance of a Maltese cross. For this examina- 
tion the object is mounted uncolored in one of the denser media 
and the light thrown directly from below. By inserting a selcnite 

87 



88 FOOD ANALYSIS 

plate between the object and the lower nicol, colors will be 
produced with many starches. Muter employed a selenite 
giving a green field, but red and red-violet fields are also suitable. 
The successful application of these methods requires good 
apparatus and considerable practice. A careful study of starch- 
granules of authentic origin should always be made before 
deciding as to the nature of any specimen. 

The size, appearance and effect on polarized light may be 
much altered by heating starch, and possibly by some other 
manufacturing operations. 

A synopsis of the characters of the principal starches is pre- 
sented in the annexed tables. A micron (o.ooi millimeter) 
may be converted into thousandths of an inch by multiplying 
by 0.03937. The factor 0.04 will be near enough for most 
cases. The classification is essentially that of ^luter, the basis 
being the predominating form of the granule, the distinctness 
and position of the hilum and markings, the appearance under 
polarized hght, with or without selenite plate. Muter indi- 
cated five groups, each group designated by the name of an 
important type of starch, as follows: 

Potato Group. — Oval or ovate granules, showing hilum 
and concentric rings clearly, cross and colors usually distinct. 

Legume Group. — Round or oval granules, hilum marked, 
rings faint, but rendered visible in cases by chromic acid solu- 
tion, cross and colors feeble. 

Wheat Group. — Round or oval granules, hilum and rings 
generally invisible, feebly-marked cross and colors. 

Sago Group. — Truncated granules, hilum distinct, faint 
rings, cross and colors fairly marked. 

Rice Group. — Polygonal granules, hilum distinct, rings 
faint, cross and colors usually faint. 

In the description of individual starches, the term "eccen- 
tric" denotes that the hilum is not in the apparent center of 
the granule. The granule is often described as oval, circular 



STARCH 



89 



or polygonal, terms which are strictly applicable to surfaces. 
It will be understood, therefore, that such terms refer to the 
apparent cross-section of the granule as it is usually viewed. 
The dimensions given must be regarded as the most frequent; 
granules not included within the limits will often be found. 
Polarized light is affected to some extent by almost all starch 
granules, if very close observation is made. 









With Po 


larizer. 




Size in 


General Character 






Source. 


Microns. 


OF Granules. 


Without Selenite. 


With Selenite. 


Potato, 


60-100 


Smaller granules round, 


Well-marked 


Well-marked 






large ones ovate; hi- 


cross. 


colors. 






lum a spot, eccentric; 










rings numerous and 










complete. 






Canna, 


45-135 


Irregular ovate; hilum 


Well-marked 


Well-marked 






annular, eccentric; 


cross. 


colors. 






rings incomplete. 










narrow and regular. 






Maranta, .... 


10-70 


Ovate; hilum eccen- 


Well-marked 


Well-marked 






tric, circular or linear. 


cross. 


colors. 






often cracked ; rings 










numerous, not very 










distinct; sometimes a 






Natal arrow- 




projection at one end. 






root, 


35-40 


Ovate to circular, ir- 
regular pro j ections ; 


Well-marked 


Well-marked 




cross. 


colors. 






hilum eccentric. 










cracked; rings dis- 










tinct. 






Turmeric, 


30-60 


Ovate, often much nar- 


Well-marked 


Well-marked 






rowed at one end; 


cross. 


colors. 






hilum eccentric, dot- 










like; rings indistinct. 






Ginger, 


40 


Ovate, many with a 
projection on one end; 
hilum and rings 
scarcely visible. 


Faint cross. 


Faint colors. 


Mother-cloves, 


20-60 


Ovate; hilum a dis- 


Well-marked 


Well-marked 






tinct spot, eccentric; 


cross. 


colors. 






rings visible. 






Banana, 


40-80 


Ovate but often very 
narrow in proportion 
to length; hilum a 
spot, eccentric; rings 
distinct. 


Faint cross. 


Faint colors. 



90 



FOOD ANALYSIS 









With Polarizer. 




Size in 


General Character 






Source. 


Microns. 


OF Granules. 


Without Selenite. 


With Selenite. 


Bean, 


35 


Reniform or ovate; 


Cross indis- 


Colors very 
faint. 




hilum stellate or fur- 


tinct. 






row-like; rings very 










faint. 






Pea, 


15-30 


Reniform or ovate; hi- 


Cross indis- 


Colors very 
faint. 




lum elongated; rings 


tinct. 






very faint. 






Lentil, 


30 


Reniform or ovate; 


Cross indis- 


Colors very 






hilum elongated, dis- 


tinct. 


faint. 






tinct; rings visible. 






Nutmeg, 


5-50 


Rounded, collected in 
groups of two to four; 
hilum stellate; rings 
invisible. 


Cross faint. 


Colors very 
faint. 


Wheat, 


2-50 


Mostly roundish, chief- 


Cross not well 


Colors very 






ly the smallest and 


marked. 


faint. 






largest sizes present; 










hilum indistinct, near- 










ly central; rings in- 










distinct. 






Barley. 


15-40 


Resembles wheat but 


Cross not well 


Colors very 






some granules slightly 


marked. 


faint. 






angular or elliptical; 










rings more distinct 










than wheat. 






Rye, 


20-60 


Resembles wheat; hi- 


Cross not well 


Colors very 






lum distinct, stellate; 


marked. 


faint. 


. 




rings often visible. 










Distorted forms not 










infrequently occur. 






Dhoura, 


1-3 


Round, hilum faint. 


Cross. 


Colors. 




12-33 


Round; no hilum. 


Cross faint. 


Colors faint. 


Acorn, 


20 


Round or nearly so; 


Cross not well 


Colors not 






hilum eccentric. 


marked. 


well 
marked. 


Cacao, 


5-10 


Round; hilum and 


Cross not well 


Colors not 






rings indistinct. 


marked. 


well 
marked. 


Sago, 


25-66 


Ovate, truncated; hi- 


Well-marked 


Well-marked 






lum a circle or spot; 


cross. 


colors. 






rings faint. 






Prepared sago, 




Characters less distinct 
than in raw sago. 






Tapioca, 


8-22 


Circular; hilum a sHt, 


Well-marked 


Well-marked 






nearly central. 


cross. 


colors. 


Prepared tapi- 










oca, 




Characters less distinct 
than in raw form. 






'W'WV^J ********* 





STARCH 



91 









With Polarizer. 




Size in 


General Character 






Source. 


Microns. 


OF Granules. 


Without Selenite. 


With Selenite. 


Cinnamon, 


8-20 


Truncated at one end, 


Well-marked 


Well-marked 






two to four granules 


cross. 


colors. 






often joined; hilum 










distinct, nearly cen- 










tral; rings invisible 






Rice, 


i;-io 


Pentasfonal, hexagonal. 


Cross distinct, 


Colors dis- 




%J 


' ■' 

occasionally triangu- 


well marked. 


tinct. 






lar with sharp angles; 










hilum distinct under 










high power. 






Buckwheat, 


5-20 


Polygonal, angles 


Cross d i s - 


Colors dis- 






somewhat rounded; 


tinct. 


tinct. 






hilum central, spot or 










star; granules often 










compound. 






Oat, 


5-30 


Mostly polygonal, a 
few spherical; hilum 


Faint cross. 


Faint colors. 












and rings visible only 










with high power; 










often compound. 






Maize, 


5-20 


Round to polygonal, 
angles usually round- 
ed; hilum central; 
crack or star; rings 
nearly invisible. 


Faint cross. 


Faint colors. 


Pepper, 


0-5 -5 


Polygonal, very small, 


Cross with 


Color Avith 






sometimes showing 


high power. 


high power. 






Brownian movement. 










sometimes united into 










large irregular masses ; 










hilum only seen with 










high power. 







According to Lintner^ potato-starch becomes pasty suddenly 
at 62-64°; cereal starches become pasty gradually at from 
80-85°. Diastase acts on ungelatinized cereal starches at 
comparatively low temperatures ; ungelatinized potato-starch is 
hydrolyzed only at a comparatively high temperature. 





\ 




liAkLKV, 



Pka. 



Bkan. 






Potato. 



Oat. 



Wheat. 






- 




'^-w 


J^£i^i^ ^ 




. ^ 


4 





® 

'^ 





Maize. 



Rice. 



Rye. 




Arrowroot. 



92 




Buckwheat. 



STARCH 93 

Determination. 

The exact quantitative determination of starch is difficult. 
The proposed methods have been carefully investigated by 
Wiley & Krug, who have shown that in the presence of vegetable 
tissue containing pentosans or similar carbohydrates the diastase 
method is alone trustworthy. The first method is applicable 
to assaying commercial starches. 

Hydrochloric Acid Method. — 3 grams of the substance 
are treated with about 50 c.c. of cold water for an hour, with 
frequent stirring ; the residue is collected on a filter and washed 
with sufficient water to make a total of 250 c.c. This liquid 
contains the soluble carbohydrates. The undissolved residue 
is heated for 2 J hours with 2.5 per cent, hydrochloric acid (200 
c.c. water and 20 c.c. hydrochloric acid, sp. gr. 1.125) in a flask 
provided with an inverted condenser, cooled, neutralized with 
sodium carbonate, made up to 250 c.c, filtered, and the dextrose 
determined in an aliquot portion of the filtrate. The weight 
of dextrose multiplied by 0.9 gives the weight of starch. 

Diastase Method. — 3 grams of the finely-powdered sub- 
stance are extracted on a hardened filter with five successive 
portions of 10 c.c. of ether, washed with 150 c.c. of a 10 per 
cent, alcohol, and then with a little strong alcohol. The 
residue is mixed in a beaker with 50 c.c. of water. The beaker 
is immersed in boiling water, the contents stirred constantly 
until all the starch is gelatinized, cooled to 55°, and 20 c.c. of 
malt-extract added. The liquid is maintained at 55° for i 
hour, heated again, boiling for a few minutes, cooled to 55°, 20 
c.c. of malt-extract added and maintained at 55° until a micro- 
scopic examination of the residue shows no starch with iodin. 
It is cooled and made up directly to 250 c.c. and filtered. 200 
c.c. of the filtrate are placed in a flask with 20 c.c. of a 25 per 
cent, solution of hydrochloric acid (sp. gr. 1.125), connected with 
a reflux condenser, and heated in boiling water for 2^- hours. It 



94 FOOD ANALYSIS 

is nearly neutralized, while hot, with sodium carbonate, made up 
to 500 C.C., mixed, poured through a dry filter, and the dextrose 
determined in an aliquot part. Calculate the dextrose to starch 
by multiplying by 0.9. 

Preparation oj Mall Exlracl. — 10 grams of fresh, finely 
ground malt are macerated overnight at about 25° with 200 c.c. 
of water, filtered, the amount of dextrose in a given quantity of 
the filtrate after boihng with acid determined as in the starch 
determination, and the proper correction noted. If diastase 
be used, a correction will be unnecessary. A good diastase 
is now easily obtainable. Commercial malt extracts are liable 
to be destitute of diastatic power. 

In the application of the diastatic method, the material 
must be ground very fine and the preliminary extraction with 
ether must not be omitted. In many cases it will be more 
convenient to make the extraction in the continuous extractor. 
If a large tube is used, several samples may be treated at once 
by tying each in filter-paper. The centrifugal apparatus may 
also be used. The fine material is shaken up with ether in the 
proper tubes, whirled for a short time, the ether poured off, 
fresh ether added and again whirled, and the operation repeated 
until the necessary amount of solvent has been used. The 
liquid may be poured off closely each time. Extraction with 
carbon tetrachlorid may be better, but the result may not be 
equivalent to that with ether. 

FLOURS AND MEALS 

Meal is coarsely ground, flour is finely ground material. 
Most of the forms used as foods are derived from plants be- 
longing to the order Graminece, but buckwheat, banana, and 
potato are not of this order. The distinction between the 
different flours and meals is based in part on the microscopic 
characters of the starches as indicated under that head, but 
chemical tests are in some cases available. 



STARCH 95 

The commercial value of wheat flour depends upon its 
color and texture and upon quantity and quality of gluten. 
The latter differs much in different varieties and in the same 
variety grown in different localities. In whole- wheat flour 
containing about lo per cent, of gluten the quantities of the 
chief proteids are about as follows : 

Globulin, 0.70 

Albumin, 0.40 

Proteose, 0.30 

Gliadin, 4.25 

Glutenin, 4.35 

Good wheat flour will yield from 20 to 40 per cent, moist 
gluten and 10 to 18 per cent, gluten dried at 100°. Rye flour 
contains gliadin, but no glutenin. 



COMPOSITION OF CEREAL GRAINS 



Typical unhulled 
barley, 

Typical American 
maize, ..... 

Typical wheat, . . . 

Sweet corn, 19 sam- 
ples (Richardson), 

Typical American 
buckwheat, .... 

Typical rye, .... 

Typical unhulled 
oats, 

Typical rice, un- 
hulled 

Typical rice, hulled, 
but unpolished, . . 

Typical rice, pol- 
ished, 

Typical rye, .... 

Typical wheat, . . . 



Weight 

OF 100 

Kernels Moist- 
in Grams, ure. 



38.0 
3.85 



3-0 
2-5 

3-0 

3-0 

2-5 

2.2 

2-5 

3.85 



10.85 
10.75 

10.6 

8.44 

12.0 
10.5 

10. o 

10.5 

12.0 

12.4 
10.5 

10.6 



6.25 

N. 



lO.O 

12.25 



10.75 
12.25 

12.0 

7-5 
8.0 

7-5 
12.25 
12.25 



Ether Crude 
Extract. Fiber. 



2.25 

4-25 
1-75 

8.57 

2.0 
1-5 

4-5 

1.6 

2.0 

0.4 
1-5 
1-75 



385 

1-75 
2.4 



10.75 
2.1 

12.0 

9.0 

i.o 

0.4 
2.1 
2.4 



Ash. 
2-. 5 

1-5 

1-75 

1.97 

1-75 
1-9 

3-4 

4.0 

1.0 

0.5 
1.9 

1-75 



Car- 
bohy- 
drates 

OTHER 

than 
Crude 
Fiber. 

69-55 

71-75 
71-25 

66.72 

62.75 
71-75 

58.0 

67.4 

76.0 

78.8 
71.7 
71-25 



A detailed description of the protcid and other constituents 
of cereal grains has been published by the United States Do- 



96 FOOD ANALYSIS 

partment of Agriculture. The table on page 95 has been taken 
from this. The proteids are calculated by multiplying the 
nitrogen by the factor 6.25, but the investigations by Osborne, 
Chittenden, and Voorhees indicate that the following factors 
would be better: Maize, 6.23; barley, rye, and w^heat, each 
5.68; oats, 6.10. A recalculation of the proteids by corrected 
factors will change the proportions of the carbohydrates, since 
these were determined by difference. 

Wheat Flour. — Good wheat flour is a fine white powder 
with a very faint yellow tinge. Several tests are recognized 
for its examination, among which are the following: 

Color Test. — The sample may be compared with one of 
known quality by laying out heaps of equal size, say, 3 cm. 
by 8 cm., and 0.5 cm. deep. If this be done on a colorless 
glass plate, the examination may be made with both white 
and colored background, and the plate may subsequently be 
immersed in water (not over 35°) so that the colors produced 
on wetting may also be observed. 

Doughing Test. — This consists in making a dough with 15 
grams of the sample and 10 c.c. of water and comparing color, 
firmness, elasticity, and compactness. 

Gluten Test. — 10 grams of the sample are mixed with suf- 
ficient water to make a stiff dough and allowed to stand for 
one hour. The mass is kneaded in a piece of linen in running 
water until the washings are clear. The fresh gluten thus 
obtained should have a faint yellow tinge, be tough and of 
such consistency that it can be pulled out into threads. Gray 
and red glutens indicate inferior samples. Good gluten swells 
at 150° and assumes the appearance of bread. 

Adulterations. — Flour may be mixed with mineral matters 
to increase weight, with alum or copper sulfate to improve 
its appearance, or ^^ith cheaper flours or starches. It may also 
contain seeds of weeds, may be damp or decomposed, or may 
contain fungi. 



STARCH 



97 



In examining for these adulterations, determintions of ash, 
crude fiber, ether extract, and total nitrogen are of consider- 
able value. The following table gives some data on these 
points, but the limits must not be rigidly interpreted. The 
figures, except the first column, have been calculated on the 
water- free substance: 

COMPOSITION OF FLOURS 



Wheat, . . . 

Rye 

Barley, . . . 
Buckwheat, 
Rice, .... 
Oat (meal), 
Maize (meal), 
Graham, . . 



Moisture. 


As 


H. 


6.25 


N. 


Fiber. 


Ether I 
Extract. 

1 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


1 
Min. 


15.0 


9.0 


0.8 


0.3 


15.0 


8.0 


1.0 


0.1 


2.0 


0.5 


14.0 


12.0 


1-5 


0..5 


1 1.0 


6.0 


0.6 


0.4 


1.0 


0.9 


15.0 


lO.O 


2.0 


I.O 


12.0 


8-.S 


0.6 


0.3 


2.0 


0.5 


18.0 


12.5 


1-5 


0.8 


9-5 


5-0 


0.6 


0.3 


2.0 


0.8 


15.0 


lO.O 


0.6 


o.,3 


10. 


7.0 


0.4 


0.1 


0.6 


0.3 


10. 


6.0 


2.4 


2.0 


18.0 


14.0 


1.4 


0.7 


9-5 


6.5 


18.0 


8.0 


4-5 


1.0 


"•5 


8.0 


3-5 


0.7 


6.0 


2.5 


15.0 


11.0 


2.2 


1.8 


15.0 


lO.O 


2.4 


2.0 


2.2 


1.9 



N-KREE 



Mill. 



90.0 
92.0 
92.0 

93-0 
90.0 
76.0 
80.0 
72.0 



82.0 
88.0 
87.0 
84.0 
85.0 
72.0 
63.0 
70.0 



Alum. 

Logwood Method. — An alkaline solution of logwood is pre- 
pared as follows : Half a gram of fine logwood chips, preferably 
freshly cut from the log, is macerated for 10 hours in 15 c.c. of 
alcohol; 10 c.c. of the solution are poured off and mixed with 
150 c.c. of water and 10 c.c. of a saturated solution of am- 
monium carbonate. To make the test, 50 grams of the flour 
are made into a thin paste with water, a few drops of the log- 
wood solution (freshly prepared) added, and the mixture 
allowed to stand several hours. Alum produces a lavender- 
blue lake. 

Chlorojorm Method. — 200 grams of flour arc shaken in a 
scparatory funnel with a sufficient amount of chloroform, 
allowed to stand overnight, and the materials which subside 
carefully removed through the stopcock. This material may 
be further purified by shaking a second time with a little chlo- 
roform and then transferred to a watch-glass and the chloro- 
form evaporated. The residue is treated with water, the solu- 



10 



98 FOOD ANALYSIS 

tion separated from ihc insoluble portion and allowed 
to evaporate, when the crystals of alum will be observed. 
The crystals may he dissolved in water and tested for sul- 
fates, aluminum, potassium, and ammonium. The residue 
insoluble in water should be examined under the microscope 
for mineral matters. The steps in the treatment of the 
residue insoluble in chloroform will be assisted by the use of a 
centrifuge. 

Copper suljaie can Ije detected by the ferrocyanid method as 
described under Bread. 

Ergot in Rye Flour. — A preliminary test may be made to 
determine if the flour has been damaged by fungi. Vogel 
advises that the sample be stained with anilin \iolet and exam- 
ined with the microscope. Any starch granules that have 
been injured by fungus will be deeply stained. 

Gruber^s test: A little of the flour is moistened with water 
on a microscope-slide, a cover-glass placed on, and the mass 
heated to the boiling-point on a hot plate or water-bath. After 
cooling it is examined with a power of 120 diameters. Ergot 
will be recognized by its high refracting power, furrows, and 
color — deep violet on the edge, greenish-yellow within. A 
second examination with a power of about 300 diameters will 
enable any doubtful particles to be recognized. 

Chemical Tests. — 200 grams of the sample are digested with 
boiling alcohol as long as any color is extracted. The solu- 
tion is treated with i c.c. of sulfuric acid (1:3). In the presence 
of ergot the solution will l^e red, and if it be diluted with a large 
volume of water, tlie color may be extracted from separate 
portions by means of chloroform, ether, petroleum spirit, or 
amyl alcohol. 

10 grams of the sample are macerated for about 30 minutes 
with a mixture of 20 c.c. of ether and 10 drops of dilute sulfuric 
acid (i : 5); the liquid filtered, washed with ether until the 
filtrate amounts to 15 c.c. This is shaken with 5 drops of a 



STARCH 99 

saturated solution of sodium bicarbonate. The chlorophyl 
remains in the ether; the sodium bicarbonate solution remains 
clear if the flour be from sound grain, but takes on a deep 
violet color if ergot be present. 

Mixed Flours. — The following data are taken, with but few 
changes, from the contributions of Bigelow & Sweetser and 
Kraemer: 

Gluten obtained from a mixture of wheat and rye flours is 
dark and viscous, without homogeneity; from a mixture of 
wheat and barley flours, dark, non- viscous, and dirty reddish- 
brown; from a mixture of wheat and oats, dark yellow; from 
a mixture of wheat and maize, yellowish and non-elastic; 
from a mixture of wheat and leguminous flour it varies from 
a grayish-red, in the case of vetch or beans, to green, in the 
case of peas, and has the characteristic odor and taste of 
leguminous products. The ash of leguminous flour is deli- 
quescent, high in chlorids, and turns turmeric paper brown; 
cereal ash is the reverse. The aqueous extract of the legu- 
minous flour is acid; that of cereal flour is faintly alkaline. 
If the filtrate from the gluten determination of flour contain- 
ing leguminous flour be made alkaline with ammonium hy- 
droxid, allowed to stand overnight, and the clear liquid de- 
canted, dilute sulfuric acid will precipitate legumin. 

For the detection of potato flour a portion of the sample is 
rubbed in a mortar until a vStiff paste is obtained, thinned with 
more water, filtered, and the clear filtrate tested with a drop of 
a dilute solution of iodin. Potato flour produces a deep blue, 
while with pure wheat flour the result is yellow or light orange. 
If a mixture of cereal and potato flours be dried, spread in a thin 
layer on a glazed black surface, and examined with a lens, the 
potato is indicated by bright and glassy particles in the other- 
wise dull white substance. 

Vogel extracts the flour with 70 per cent, of alcohol, to 
which 5 per cent, of hydrochloric acid has been added. The 



lOO FOOD ANALYSIS 

extract is colorless if the Hour consist only of wheat or rye, pale 
yellow if adulterated with barley or oats, orange yellow with pea 
flour, purple red if made from mildewed wheat, and blood red 
if made from crgotized wheat. 

Kicc in Buckwheat Flour. — When pure buckwheat is mixed 
with water into a thin paste, the addition of calcium hydroxid 
produces a dark green, which becomes red when acidified with 
hydrochloric acid. Rice flour gives a yellow color with potas- 
sium hydroxid and white with hydrochloric acid. A mixture 
of buckwheat and rice flours made into paste is changed to a 
light green color by potassium hydroxid and becomes flesh- 
colored when acidified with hydrochloric acid. 

Wheat in Rye Flour. — Kleeburg has advised the follow- 
ing test: A pinch of the sample is mixed on a small glass 
plate (a microscope-slide will serve) with w;ater at about 45° 
in sufficient quantity that the particles of flour still float. The 
mixture is spread over a considerable part of the glass and a 
similar glass laid upon it so that about one-fourth of each 
glass protrudes at the ends. The two glasses are pressed 
together, the exuded liquid wiped off, and the glasses rubbed 
on each other several times. If wheat flour be present, white 
spots will be observed, which will form threads on being rolled; 
these are short and thin if the proportion of wheat be small, 
and thicker and longer with larger amounts. An admixture 
of 5 per cent, of wheat flour with rye is said to be thus recogniz- 
able. 

Maize in Wheat Flour. — Kraemer has devised the follow- 
ing test, which, he states, will detect 5 per cent, of maize in 
wheat flour: i gram of the sample is mixed with 15 c.c. of 
good glycerol and heated to boiling for a few minutes. An 
odor recalling that of popcorn indicates maize. 

It is alleged that cheap flours have been adulterated with 
sawdust. G. A. LeRoy applied the following test for detect- 
ing this addition: A small amount of the sample is gently 



STARCH lOI 

warmed with the acid solution of phloroglucol (page 26). 
Ordinary wood-fiber quickly acquires a bright red tint, while 
bran particles are but slightly affected. 

BREAD 

Bread is made by baking the mass obtained by kneading 
flour with water. This gives the so-called unleavened bread, 
but it is usual to add a little common salt to the water and 
make the dough light by inflating it with carbon dioxid. This 
may be done by the use of baking powder, or by mixing the 
flour with water containing carbonic acid under pressure (aer- 
ated bread), but commonly yeast is added to the dough and the 
mixture, called the ''sponge," allowed to stand for some hours 
and then baked. The slight fermentation which occurs liber- 
ates carbon dioxid. 

The chemical composition of bread is approximately that of 
the flour from which it is made. The moisture usually ranges 
from 30 to 40 per cent., and will depend, among other condi- 
tions, upon the quantity and quality of the gluten, and the 
size and shape of the loaf. On the size and shape will also 
depend the relative proportion of crust to crumb, the latter 
containing about twice as much moisture as the former. The 
addition of potato flour or rice flour will enable a bread to be 
prepared containing a much larger proportion of water than 
usual. The addition of about i per cent, of mashed potatoes 
to the dough is said to render the bread white without any 
notable increase in the amount of moisture retained. 

The proportion of fat in bread, as determined by the ether 
extract, is apt to be less than that of the original flour, owing 
to decomposition of the fat in the crust, by heat, and also to 
the inclosurc of the fat particles in such a way as to render 
them diflicult of extraction. On the other hand, the propor- 
tion of fatty matter may be increased by the use of milk or by 
the material used to grease the pans. 



I02 



FOOD ANALYSIS 



When bread is raised by yeast, some solid matter is lost by the 
fermentation. According to Lawes and Gilbert, this is prob- 
ably less than J of i per cent., and appears to be due to the 
decomposition of the sugar. The unchanged starch is not 
appreciably altered during the short time that the yeast acts. 
The ash of bread will be higher than thai of the flour if salt 
or baking powder has been added. 



Orig- 
inal 
Sub- 
stance 



Pro- 
Moist- ! teids, 
ure. N X 
5-70. 



3441 



23 



Vienna, average of 10 sam- 
ples, 38.71 

Homemade, average c>f 2 
samples, 33-02 10.8 

Graham, average of 9 sam- 1 

pies, 34.8 I 12.51 

Rye, average of 7 samples, j ;^^ 42 11.86 

Quaker, average of 3 sam- ' 

pies, 36.16 

Miscellaneous, average of 
9 samples, ... 



II. I" 



In thk Dry Substance. 



Ether 
Ex- 
tract. 



1-73 
2.91 

1.02 

1-75 



Crude 
Fiber. 



Ash. 



0.97 1.95 
036 i 1.55 



Salt. 



0-93 
0.84 



Carbo- 

by- 
(hatfs. 
exchicl- 

iiig 
Fiber. 



83.1 
84.75 



1.74 2.29 1.07 82.06 
095 I 2.79 1.5 84.36 

0.41 1.68 0.92 85.41 



10.59 ' 2.21 , 0.46 1.53 I 0.76 85.66 



The tabic represents the average composition of various 
breads of commerce according to analyses published l^y the 
Department of Agriculture. The loaves weighed approximately 
one pound each. Trade names are given in most cases. 

Adulterations. — These may consist in the use- of damaged 
flour, of flours other than that purporting to be present, presence 
of excess of water, or addition of alum or copper sulfate to 
improve appearance. 

Alum. — The bread is moistened with water and then with 
some of the alkaline logwood solution (see p. 97). If alum be 



STARCH 103 

present, the bread will become lavender-blue in an hour or 
two. Pure bread assumes a light, red-brow^n tint. The blue 
color, however, is not proof of the presence of alum unless 
it is permanent at the temperature of boiling water. 

Blyth gives the following test: 150 grams of the material 
are macerated for two days in 2 liters of water. The solution 
is strained through muslin and evaporated at a gentle heat to 
small volume; a strip of gelatin immersed in this liquid, and 
then in the alkaline logwood solution, will acquire the lavender 
color if alum is present to the extent of 0.03 per cent. 

These tests are not applicable to sour bread. Vander- 
planken recommends the following modification to meet the 
difficulty: 15 grams of the sample are triturated to a paste 
with water and some pure sodium chlorid and 10 drops of 
a freshly-prepared solution of logwood in alcohol, and then 
5 grams of pure potassium carbonate are added. The mass is 
well mixed, washed with 100 c.c. of water into a beaker, and 
is allowed to settle. In a few minutes the liquid becomes 
reddish-violet if alum is absent, grayish-blue to deep blue 
when it is present. 

The quantitative estimation of the alum is made as follows: 
The ash from 100 grams or more of the bread is boiled with 
hydrochloric acid and the solution filtered. The filtrate is 
boiled and added to a concentrated solution of sodium hy- 
droxid, the mixture being again boiled and filtered while hot. 
A little disodium acid phosphate is added to the filtrate, which 
is then slightly acidulated with hydrochloric acid and finally 
made feebly alkaline by addition of ammonium hydroxid. Tlic 
precipitate of aluminum phosphate is filtered, washed, ignited, 
and weighed. Flour contains a small proportion of aluminum, 
which, in the ash, is probably in the form of silicate. The 
amount of silica is approximately equal to that of alum equiva- 
lent to the aluminum normally present. It is the practice, 
therefore, to determine the silica and suljtract it from tlic 



I04 FOOD ANALYSIS 

amount of alum calculated from the aluminum phosphate found. 
The remainder, multiplied by 3.8 or 3.7, will give approximately 
the potassium alum or ammonium alum respectively. 

Copper suljatc may be detected by the brown produced 
when a thin slice of bread is immersed in a dilute solution of 
potassium ferrocyanid. 

Foreign flours may be sought for by the microscope, but 
the starch granules are usually so altered by heat as to render 
identification impossible. 

Y(.)Y detection of maize in wheat bread and pastry, Ottolenghi 
proposes the following test based on the reaction of proteids 
peculiar to maize as elucidated by Donard & Labbe.^ 

100 grams of crumb are dried at 40°, powdered finely, treated 
with 500 c.c. of a 0.3 per cent, solution of potassium hydroxid 
for 12 hours, with frequent shaking. The liquid is strained 
through muslin, the residue again treated with the alkaline 
solution for 3 hours, after which the mass is poured on the muslin 
strainer and well pressed. The filtrate is evaporated below 
70° to dryness, the residue broken up as finely as possible, 
transferred to a flask, mixed with 40 c.c. absolute iso-amyl 
alcohol, an inverted condenser is attached to the flask and the 
liquid boiled in an oil-bath for 6 hours. The solvent is filtered 
hot. If no maize is present, the yellowish-brown filtrate re- 
mains clear, but with maize it becomes turbid. The admixture 
of the filtrate with 3 volumes of pure benzene increases the tur- 
bidity if maize is present, but produces no effect if the original 
substance was pure wheat flour. 

The following adulterants are said to be employed abroad, 
but their use does not appear to have been attempted in this 
country : 

Soap is said to be used to render the bread light and soft. 
It is said to be added in solution containing emulsified oil. 

Terra alba and gypsum have been found; they are readily 
detected in the ash. 



LEAVENING MATERIALS I05 

Stannous chlorid is a common constituent of ginger cake, to 
which it is added, with potassium carbonate, in order to give 
the product the color ordinarily produced by honey or mo- 
lasses. It is said to render a product made of poor flour and 
molasses of the same color as that produced by a good flour 
and honey. Tin may be detected as described on page 59. 

LEAVENING MATERIALS 

The yeast cakes sold for leavening purposes are usually 
mixtures of common yeast with potato starch. The study 
of yeast is practically limited to those connected with the 
fermentation industries. Cream of tartar and baking soda are 
commonly employed as leavening agents. 

Baking Soda, Sodium Acid Carbonate, is not subject to 
serious adulteration. 

Cream of Tartar, Acid Potassium Tartrate, is frequently 
adulterated with starch, alum, acid calcium phosphate, calcium 
sulfate, and potassium acid sulfate. Many samples will be 
found to contain no tartrate, but merely a mixture of starch, 
calcium phosphate, and alum. 

For the detection of tartaric acid see under "Fruit Juices." 
If starch is present the sample should be treated with cold 
water for a w^hile, filtered and the residue evaporated on the 
water bath and tested. 

Allen devised the following method for the examination of 
commercial cream of tartar : 

1. 881 grams of the dried material are dissolved in hot water 
and titrated with — - sodium hydroxid and phenolphthalein. 
If tartaric acid and acid sulfates are not present, each c.c. will 
represent i per cent, of acid potassium tartrate. 

1. 881 grams of dried material are ignited for 10 minutes, 
the residue boiled with water, filtered, and washed. The 

filtrate is titrated with ^^ hydrochloric acid and methyl-orange. 



Io6 FOOD ANALYSIS 

With pure tartrate the amount of acid consumed will be the 
same as that of the alkali in the first experiment. Each cubic 
centimeter of deficiency is eciuivalent to 0.36 per cent, calcium 
sulfate, or 0.72 per cent, acid potassium sulfate. If the amount 
of acid be more than equivalent to that of the alkali used in the 
former experiment, it suggests the presence of neutral tartrate, 
each cubic centimeter of excess representing 0.6 per cent, thereof. 
The amount of sulfate can be determined by precipitating with 
barium chlorid in the usual way. 

The residue is ignited, dissolved in 20 c.c. of 7^ acid, filtered 
from any insoluble residue, and the filtrate titrated with -^^ 
alkali. Each c.c. corresponds to 0.5 per cent, of calcium 
tartrate, or 0.36 per cent, of anhydrous calcium sulfate. 

The cream of tartar substitutes commonly sold contain 
starch, alum, and calcium })hosphate. Starch can be detected 
by the iodin test and by the microscope. Quantitative examin- 
ation of such samples will be conducted as described under 
"Baking Powders." 

Baking Powders. — These contain acid sodium carbonate, 
some acid salt, e. g., acid potassium tartrate, acid calcium 
phosphate, or alum, with inert material, starch or flour, to 
prevent caking. Alany powders contain both alum and acid 
calcium phosphate. The following methods for examining 
baking powders were published by Crampton : 

The value of leaking ])owder depends on the gas liberated 
when it is mixed with water. The determination may be 
by the apparatus of Knorr (figure 34). The flask A holds the 
weighed portion of sample. The condenser D, attached by a 
ground joint, serves to condense the steam formed when the 
liquid in A is boiled. B contains either recently-boiled water or 
dilute sulfuric acid, according to whether the available carbon 
dioxid or total carbonates are to be determined. 

It has a soda-lime tube attached by a ground-joint to pre- 



LEAVENING MATERIALS 



107 



vent admission of carbon dioxid from the current of air which 
is drawn through the apparatus during the operation. The 
junction of this portion with the flask should be by ground 
or fused joint. The evolved gas is dried in E by sulfuric 
acid and absorbed in F. 




Fig. 



34. 



Available carbon dioxid, which gives the leavening power, 
is determined as follows: The flask A is dried thoroughly, 
a weighing tube is charged with about 2 grams of the powder, 
accurately weighed, the contents emptied into the flask, and 
the tube weighed again. The exact amount of powder taken 



Io8 FOOD ANALYSIS 

is thus known. Rcccntly-boilcd water is put into B, the 
apparatus connected tightly, and the water allow^ed to flow in 
slowly from B, the aspirator attached to G being put in opera- 
tion. When the etTervescence in A has ceased, the liquid in it is 
boiled for a few seconds, the lamp removed, and aspiration 
through G continued for 15 minutes. The absorption ap- 
paratus F is w^eighed, and the increase represents carbon dioxid. 
Total carbonates arc determined bv substituting; 10 c.c. dilute 
sulfuric acid for the water in B. 

Starch. — 5 grams are mixed in a flask with 200 c.c. of 4 per 
cent, hydrochloric acid. A condensing tube about i meter 
long is attached by means of a cork (an inverted condenser may 
be used) and the liquid boiled for 4 hours. The contents are 
cooled, rendered slightly alkaline by sodium hydroxid, and the 
dextrose determined as given, and multiplied by 0.9. 

For powders not containing appreciable amounts of alum, 
direct washing with water, and drying the residue, will often 
give determinations of sufficient accuracy. Since the residual 
liquid in properly-made baking powders is alkaline, due to 
slight excess of baking pow^der, the diastase method for starch 
may be applicable. The liquid should be filtered and the 
insoluble residue well washed. The aluminum hydroxid may 
interfere with this method. If flour be used as filler, w^hich 
may be ascertained by inspection, the starch found may be 
roughly calculated to flour by the table on page 97. 

Aliimhium and Phosphates. — ^McElroy devised the following 
method: 5 grams are charred in a platinum basin, mixed with 
strong nitric acid, and filtered into a 500 c.c. flask. The 
residue is washed slightly, the filter and residue returned to 
the basin, burned to whiteness, mixed with sodium carbon- 
ate, fused, and cooled. Nitric acid is added, the liquid evapo- 
rated to dryness, again acidified with nitric acid, and the whole 
mass washed into the 500 c.c. flask. The liquid is made up to 
the mark and filtered through a dry filter, 100 c.c. of the filtrate 



LEAVENING MATERIALS IO9 

are nearly neutralized with ammonium hydroxid, ammonium 
nitrate and ammonium molybdate solution added, the mass 
digested at a low heat for a few hours, and filtered. The 
filtrate contains the aluminum, which may be precipitated 
as hydroxid by adding ammonium hydroxid. The precipitate 
is dissolved in ammonium hydroxid and the phosphate deter- 
mined in the usual way. 

Calcium. — 5 grams are mixed in a 500 c.c. flask with 50 
c.c. of water and 30 c.c. of strong hydrochloric acid, the mixture 
made up to the mark, shaken well, and allowed to settle. 50 
c.c. are collected through a dry filter, nearly neutralized by 
ammonium hydroxid, acetic acid added in small amount, then 
ammonium acetate, and the liquid boiled. If any precipitate 
forms it should be removed. The clear liquid is precipitated 
by ammonium oxalate. 

Sulfates. — 0.5 gram of the sample are digested with strong 
hydrochloric acid until everything has dissolved, the liquid is 
diluted considerably, brought to boiling, and precipitated with 
barium chlorid, taking care not to use a large excess. The 
precipitate is weighed in the usual manner. 

Ammonium Compounds. — These may be determined by 
adding to the water filtered from a known weight of the powder 
sufficient sodium carbonate to make it distinctly alkaline 
distilling until half the liquid has passed over and titrating 
the distillate with standard acid. 

The best commercial baking powders yield about 12 per 
cent, by weight of gas. 10 grams would, therefore, yield 1.2 
grams, occupying at ordinary temperature about 600 c.c, 
which will be much increased in baking. Many powders 
yield much less gas. 



no FOOD ANALYSIS 

SUGARS 
Detection. 

Most of the tests for sugars except the phenylhydrazin, fer- 
mentation, and optic tests depend on their reducing effect. Su- 
crose possesses less reducing action than other common sugars, 
does not give any precipitate with phenylhydrazin, and is not 
directly femientable. By the action of dilute acids or inver- 
tase (yeast-enzym) it is converted (hydrolyzed) to equal parts 
of dextrose and levulose, a change commonly termed "in- 
version," the mixture being known as "invert-sugar." This 
responds to all the above tests. 

Cobalt Nitrate Test. — Wiley has experimented with this 
method and has obtained satisfactory results. He describes 
it as follows: 

5 c.c. of a 5 per cent, solution of cobaltous nitrate are well 
mixed with 15 c.c. of sugar solution, and 2 c.c. of a 50 per 
cent, solution of sodium hydroxid added. Sucrose gives an 
amethyst-violet solution, which is made somewhat more blue 
by boiling, but regains its color on coohng. Dextrose gives 
a turquoise-blue, which in the course of two hours passes into 
a pale green. A slight flocculent precipitate is noticed in the 
tube containing dextrose. Maltose and lactose act very much 
as dextrose, but in the end do not give so fine a green color. 
If the solution containing dextrose, lactose, or maltose be 
boiled, the original color is destroyed and a yellow-green 
color takes its place. In mixtures of dextrose and sucrose 
the sucrose coloration predominates — one part of sucrose in 
nine parts of dextrose can be distinguished. Impurities such 
as gum arabic or dextrin should be removed by alcohol or 
lead subacetate before the application of the test. Dextrin 
may also be thrown out by treatment of the solution with 
barium hydroxid and ammoniacal lead acetate. The reaction 
may be applied to the detection of cane-sugar in wines after 



SUGARS . Ill 

they are thoroughly decolorized by means of lead acetate and 
bone-black. Sucrose may be detected in fresh or condensed 
milk after the disturbing matters have been thrown out by lead 
acetate. Sucrose may be detected in honey. 

Phenylhydrazin Test. — Phenylhydrazin hydrochlorid is usu- 
ally employed. The commercial article is often contaminated 
with anilin hydrochlorid. It may be purified by solution in hot 
water, precipitation by strong hydrochloric acid, and recrys- 
tallization from hot water. 

For the test, o.i gram of the sample, about 0.2 gram phenyl- 
hydrazin hydrochlorid, and 0.3 gram of sodium acetate are 
dissolved in 5 c.c. of water and heated on the water-bath for 
some time. Sucrose forms no precipitate, but with many 
sugars crystalline compounds called osazones separate. 

Dextrose and levulose yield the same compound, which 
may be termed "glucosazone." It crystallizes in needles 
melting at 204-205°, and reduces Fehling's solution. 

Maltosazone crystallizes in plates that melt with decomposi- 
tion at 206°. 

Lactosazone crystallizes in prisms melting at 200°. 

Sucrose forms no osazone. After hydrolysis it yields glu- 
cosazone. 

Lactose, after boiling with dilute sulfuric acid, yields a mixture 
of glucosazone and galactosazone. The latter is distinguished 
by its melting-point, 193°. 

Starch and dextrin, after hydrolysis, yield maltosazone and 
glucosazone. 

Maltose and lactose produce with ammonium hydroxid a 
characteristic red, a reaction that distinguishes them from other 
common carbohydrates. Wohlk,^^ to whom this test is due, 
describes the following manipulation: 

About 0.6 gram of the sample are dissolved in a test tube in 
10 c.c. of 10 per cent, ammonium hydroxid and the tube im- 
mersed in water that has just ceased boiling. This causes the 



112 FOOD ANALYSIS 

ammonium hydroxid lo pass off without the liquid rcacliing the 
boiling-point or being ejected. In about 20 minutes the color 
appears. 
Determination. 

The preparation of sucrose for use as a standard in polar- 
imetry and reduction-tests was the subject of formal action 
at the third session of the International Commission jor Uni- 
form Methods oj Sugar Analysis, Paris, July 24, 1900. 

Purest commercial sugar is selected and dissolved bv satu- 
ration in hot water, and ethyl alcohol added sufficient to pre- 
cipitate the sugar. The precipitate is whirled in a centrifuge 
and washed with alcohol. The material obtained is put through 
the whole process a second time, and the w^ashed material is 
dried on pure bibulous paper and kept in stoppered glass ves- 
sels. It still contains moisture, which must be determined 
and allowed for in making standard solutions. 

The temperature of the water is not given. Blotting-paper 
is mentioned in the original test, but filter-paper is better, as 
commercial blotting-paper is of uncertain composition. 

For the standardization of solutions for the determination of 
sucrose and invert-sugar, 2.5 grams of pure sucrose should 
be dissolved in a mixture of 75 c.c. of water and 5 c.c. of hy- 
drochloric acid (sp. gr. 1.188 at 15°), hydrolyzed according 
to the method on page 119, the acid neutralized with sodium 
carbonate, and the solution diluted to one liter. 2.5 grams of 
sucrose yield 2.6316 grams of invert-sugar. The number of 
cubic centimeters of sugar solution used, multiplied by 0.00263, 
will give the weight of invert-sugar required to reduce com- 
pletely 10 c.c. of the test solution under the conditions of the 
experiment. 
chemical methods. 

These methods, when applied to the determination of sucrose, 
must be preceded by hydrolysis, for which see page 119. 

The following are standard reagents : 



SUGARS 113 

soxhlet's modified copper solution (a. o. a. c). 

Copper sulfate solution. 34.639 grams of pure crystallized 
copper sulfate are dissolved in sufficient water to make 500 c.c. 

Alkaline tartrate solution. 173 grams of pure potassium 
sodium tartrate and 50 grams of sodium hydroxid are dis- 
solved in sufficient water to make 100 c.c. A convenient 
method is to use 100 c.c. of a solution containing 500 grams 
of sodium hydroxid in one liter. 

Potassium acid tartrate, now obtainable of very good quality, 
may be used instead of potassium sodium tartrate, in which 
case the proportion required will be 133 grams of potassium 
acid tartrate and 80 grams of sodium hydroxid made up to 500 
c.c. The copper and alkaline tartrate solutions must be kept 
separate in well-stoppered bottles and mixed only when needed. 

APPROXIMATE VOLUMETRIC METHOD FOR RAPID WORK. 

5 C.C. of each of the solutions are placed in a large test-tube, 
10 c.c. of distilled water added, the liquid heated to boiling, 
and small portions of the solution to be tested gradually added 
until the copper has been completely precipitated, boiling to 
complete the reaction after each addition. When the end 
reaction is nearly reached and the amount of sugar solution 
can no longer be judged by the color of the solution, a small 
portion of the liquid is removed by means of a filtering-tube, 
placed in a porcelain crucible or on a testing plate, acidified 
with dilute acetic acid, and tested for copper by solution of 
potassium ferrocyanid. The sugar solution should be of such 
strength as will require from 15 to 20 c.c. to complete the 
reduction, and the number of additions of solution should be 
as few as possible. It is best to verify the first experiment 
by a second, based on the approximation which the first gives. 
Boiling for 2 minutes should be required for complete precipi- 
tation when the full amount of sugar solution has been added in 
one portion. The factor for calculation varies witli tlic minute 
details of manipulation; every operator must dclcrminc the 
II 



114 



FOOD ANALYSIS 



individual factor by using a known amount of the form of sugar 
that is to be determined and maintaining conditions as uniform 
as possible. 

Figure 35 shows filter-tubes suitable for obtaining a small 
quantity of the liquid. Wiley's tube (A) is a thick-walled glass 
tube about 4 cm. long on one of which a flange has been made, 
over which a piece of fine linen is tied. Knorr's tube (B) is 
much narrower, and has a perforated platinum 
disk sealed into the lower end. The tube is 
dipped into water containing suspended asbes- 
tos, and by aspiration a thin felt is formed over 
the lower surface of the platinum disk. The 
tube, thus prepared, is dipped into the boiling 
copper solution and by aspiration a drop is 
drawn into the tube. The Wiley filter requires 
that the liquid be poured from the tube when 
it is to be tested, but with the Knorr tube the 
asbestos is wiped off, the liquid expelled through 
the platinum, and the drop is tested for copper 
as noted. 

Another method is to remove a drop of the 

E boiling solution by means of a rod and place 

it on a piece of pure filter-paper. The pre- 

IH^ (@) cipitate remains in the center of the moistened 

^^ g spot. A drop of potassium ferrocyanid solu- 

FiG. 35. tion, acidulated with acetic acid, is then placed 

near it ; as the spot spreads, a brown stain will 

appear where the liquids meet, if copper still be in solution. 

soxhlet's exact method. 

An approximate determination of the reducing sugars in 
the sample is made by one of the titration methods and a 
solution is prepared which contains nearly, but not more than, 
I per cent, of these sugars. 50 c.c. of copper sulfate solution 
and 50 c.c. of alkaline tartrate solution are mixed, added to a 



SUGARS 



II 



volume of the solution of the sample estimated to be suffi- 
cient for the complete precipitation of the copper, boiled for 
2 minutes, some of the solution filtered rapidly, and the filtrate 
tested for copper. The process is repeated until two proportions 
of the solution of the sample are determined which differ by 
O.I C.C., one giving complete reduction and the other leaving 
a small amount of copper in solution. The means of these 
volumes is the amount of solution required for the volume of 
Fehling solution taken. 

Under these conditions, which must be rigidly observed, the 
volume of solution used will contain 0.475 gram 
of dextrose or 0.494 gram of invert-sugar. As 
the weight of the sample which is in this amount 
of solution is known, the percentage of either 
sugar may be calculated by simple proportion. 
allihn's method for dextrose. 

Copper sulfate solution. See page 113. 

Alkaline tartrate solution. 173 grams of pure 
potassium sodium tartrate and 125 grams of 
potassium hydroxid are dissolved in water and 
made up to 500 c.c. 

The substance to be tested is dissolved in 
water in such proportion that the solution shall 
not contain more than i per cent, of dextrose. 
30 c.c. of each of the reagent solutions and 60 c.c. of water are 
mixed and heated to boiling, 25 c.c. of the solution to be exam- 
ined are added, the boiling continued for 2 minutes, and the liquid 
immediately filtered without dilution, as directed in connection 
with the reduction or electrolytic methods of determination of 
copper. 

The precipitated cuprous oxid is usually converted into free 
copper and weighed as such. Two methods may be employed 
for reduction: by hydrogen or by electrolysis. 

Reduction by Hydrogen. — The cuprous' oxid is collected on an 



Fig. 36. 



Il6 FOOD ANALYSIS 

asbestos filter. This is arranged most conveniently in a special 
filtering tube, which is shown in figure 36. The wider part is 
about 8 cm. long and 1.5 cm. in diameter, the narrower portion 
about 5 cm. long and 0.5 cm. in caliber. A perforated platinum 
disk is sealed in just above the point of narrowing. The asbes- 
tos is placed on this disk, washed free from loose fibers, dried 
well and the tube weighed. The filtering tube is attached to an 
exhaustion apparatus by passing narrower portion through the 
cork, and a small funnel is fitted tightly in the top of the tube. 
The object of this funnel is to prevent the precipitate collect- 
ing on the upper part of the tube. The lower end of the 
funnel should project several centimeters below the bottom of 
the cork through which it passes. 

The filtering apparatus must be arranged prior to the pre- 
cipitation, so that the cuprous oxid may be filtered without 
delay. The precipitate is transferred as rapidly as possible 
to the filter, wtII washed with hot water, alcohol, and ether 
successively, dried, and the cuprous oxid reduced by gentle 
heating in a current of dry hydrogen. When the reduction 
is complete, the heat is withdrawn, but the flow of hydrogen 
is continued until the tube is cold. It is then detached and 
weighed. The amount of sugar is determined by reference to 
the table on page 117. Quantities of copper intermediate be- 
tween those given in the table may be converted into the equiva- 
lent in sugar by allowing for each o.ooi of copper, 0.0005 of 
dextrose for figures in the first column, 0.00055 for figures in the 
second column, and 0.0006 in the third column. 

Reduction oj Copper by Electrolysis. — The filtration is per- 
formed in a Gooch crucible with an asbestos-felt film and the 
beaker in which the precipitation was made is well washed 
willi hot water, the washings being passed through the filter, 
Init it is not necessary to transfer all the precipitate. When 
the asbestos film is completely washed, it is transferred with 
the adhering oxid to the beaker; any oxid remaining in the 



SUGARS 



117 



crucible is washed into the beaker by use of 2 c.c. nitric acid 
(sp. gr. 1.42), added with a pipet. The crucible is rinsed 
with a spray of water, the rinsings being collected in the beaker. 
The liquid is heated until all the copper is in solution, filtered, 
the filter washed until the filtrate amounts to at least 100 c.c, 
and electrolyzed. 





EQUIVALENTS FOR 


ALLIHN'S 


METHOD 




Copper. 


Dextrose. 


Copper. 


Dexirose. 


Copper. 


Dextrose. 


O.OIO 


0.0061 


0.170 


0.0869 


0.330 


O.173I 


0.020 


o.oi 10 


0.180 


0.0921 


0.340 


0.1787 


0.030 


0.0160 


0.190 


0.0973 


0.350 


0.1843 


0.040 


0.0209 


0.200 


0. 1026 


0.360 


0.1900 


0.050 


0.0259 


0.210 


0.1079 


0.370 


0.1957 


0.060 


0.0308 


0.220 


O.II32 


0.380 


0.2014 


0.070 


0.0358 


0.230 


O.II85 


0.390 


0.2071 


0.080 


0.0408 


0.240 


0.1239 


0.400 


0.2129 


0.090 


0.0459 


0.250 


0.1292 


0.410 


0.2187 


0. 100 


0.0509 


0.260 


0.1346 


0.420 


0.2245 


0. no 


0.0560 


0.270 


0. 1400 


0.430 


0.2304 


0.120 


0.061 1 


0.280 


0.1455 


0.440 


0.2363 


0.130 


0.0662 


0.290 


0.I5I0 


0.450 


0.2422 


0.140 


0.0713 


0.300 


0.1565 


0.460 


0.2481 


0.150 


0.0765 


0.310 


0.1620 


0.463 


0.2499 


0. 160 


0.0817 


0.320 


0.1675 


0.465 


0.2511 



Electrolytic apparatus has been constructed in a great variety 
of forms. When the operation is carried out frequently, it is 
best to have an electrolytic table. A platinum basin holding 
not less than 100 c.c. is used. A cylindrical form with flat 
bottom is convenient. It should rest on a bright copper plate, 
which is connected with the negative pole of the electrical 
supply. The positive pole should be also platinum, either a 
spiral wire, cyHndcr, or flat foil. Many operators use a funnel- 
shaped perforated terminal for the negative pole; in which case 
a glass beaker or casserole will be a suitable container, the posi- 
tive terminal being placed within the negative. 



Il8 FOOD ANALYSIS 

Four cells of a gravity battery will suffice for a single de- 
composition, and will operate two, but more slowly. It is 
usual to arrange the apparatus so that the operation may be 
continued during the night. When the electricity is taken 
from the general supply of the laboratory, it is usually neces- 
sary to interpose resistance and to have some means of meas- 
uring the current-flow. This is sometimes done with a gas 
evolution cell and incandescent lamp, but an ammeter and 
adjustable rheostat is better. 

OPTIC METHODS. 

The general principles of polarimetry have been explained 
elsewhere. For the decolorization and clarification of solu- 
tions, the following standard reagents are employed : 

Lead suhacetate. Solution of lead acetate is boiled with 
excess of lead monoxid for 30 minutes, filtered, and brought 
to a specific gravity of 1.250. Solid lead subacetatc may be 
used in preparing the solution. 

The clarification of sugar solutions may often be more con- 
veniently effected by the addition of solid lead subacetate, ac- 
cording to the suggestion of Horne.^^ The weighed material is 
dissolved in water and made up to 100 c.c. Finely-powdered 
lead subacetate is added in small cjuantities, with shaking until 
the precipitation is complete, allowing each portion to dissolve 
before adding more. When the last portion has dissolved, 
the solution is shaken, filtered and the reading taken. No 
allowance for precipitate is required. 

Excess of lead may be removed from these solutions by 
Sawyer's method.^- A solution of double normal potassium 
oxalate (184.4 grams in 1000 c.c.) is used. 10 c.c. of this are 
added to 80 c.c. of the clarified solution, allowed to stand at 
room temperature for 15 minutes, and filtered. The oxalate 
is in large excess; this does not interfere with the polarization 
but renders the preci})ilcite granular and easily filtered. 

Alumina-cream. A cold saturated solution of alum is 



SUGARS 119 

divided into two unequal portions; a slight excess of ammo- 
nium hydroxid is added to the larger portion and the remainder 
is added until a faintly acid reaction is obtained. 

For sugars and molasses the normal weight for the instrument 
is weighed out, washed into a 100 c.c. flask, and water added to 
make about 80 c.c. When the material has dissolved as far as 
possible, lead subacetate is added until all precipitable matter 
has separated. (With molasses sufficient acetic acid should be 
added to convert the lead subacetate into acetate.) The flask 
is filled to the mark, — using, if necessary, a little ether spray to 
break bubbles, — filtered with a dry filter, the first 15 c.c. re- 
jected, and the reading taken on the remainder of the filtrate. 
If the liquid is very dark, some dry finely-powdered pure bone- 
black should be used instead of paper and the first 40 c.c. of 
filtrate rejected. All observations should be made as nearly as 
possible at the temperature for which the instrument is adjusted. 
A change of 5° in the interval between filling the flask and 
making the reading will cause, by change of volume, an error of 
about 0.1 per cent, in samples containing 90 per cent, of sucrose 
and an error of about 0.5 per cent, in samples containing 50 per 
cent, of sucrose. 

With juices or other dilute materials, weighing may be 
omitted, and 100 c.c. of the sample measured off, powdered lead 
subacetate added (page 118), filtered and a reading taken. 

A. O. A. C. INVERSION METHOD (hYDROLYSIS). 

A clear solution is made according to one of the methods 
given above. 50 c.c. of the filtrate are placed in a flask marked 
at 50 and 55 c.c, 5 c.c. of pure fuming hydrochloric acid added, 
and the liquids well mixed. The flask is heated in water until 
the thermometer, with the bulb as near the center of the solution 
as possible, marks 68°. About 15 minutes should be required 
for this heating. The flask is then removed, cooled quickly 
to room temperature, and polarized, noting the temperature. 
If the sample originally contained invert-sugar, the secoud 



I20 FOOD ANALYSIS 

polarization should he made at approximately the same tem- 
perature as the first. The calculation of the amount of sucrose 
is made h\' llie followimr formula: 



'ft 



Q a dz h 

2 

a being the first and b the second reading, which are added 
when of opposite signs and subtracted when of like signs; 
that is, the algebraic difference is taken, in either case. 

With dark-colored materials it will often be advantageous 
to add an excess of alumina cream. Alumina cream alone 
will often suffice for clarification. 

When lead subacetate is used with liquids containing levu- 
lose, it is usual to render the filtrate acid in order to break 
up a compound which the levulose forms with lead, but it is 
likely that potassium oxalate method (page ii8) would be satis- 
factory. 

Hydrochloric acid affects slightly the rotatory power of these 
solutions. In observations at high temperatures, the expansion 
of the liquid also introduces an error. These interferences 
are usually disregarded in food analysis. 

GERMAN OFFICIAL METHOD. 

26.048 grams of the sample are dissolved in a sugar flask and 
the solution made up to 100 c.c; 50 c.c. of this solution are 
transferred by means of a pipet to a flask graduated at 50 and 
55 c.c, enough lead subacetate solution added for clarification, 
the volume made up to the 55 c.c. mark, and the liquid thor- 
oughly shaken and filtered. The filtrate is then polarized, the 
reading being corrected for the extra 5 c.c. The liquid ad- 
hering to the pipet is washed into the 100 c.c. flask containing 
the remaining 50 c.c. (13.024 grams), 5 c.c. of concentrated 
hydrochloric acid (38 per cent., specific gravity 1.188 at 15°) 
added, and the flask placed in a water-bath the temperature of 



SUGARS 121 

which is 70°. The contents of the flask should reach a tem- 
perature of 67^-70° in two or three minutes, when the tem- 
perature should be maintained within this limit for exactly five 
minutes, keeping the temperature as nearly 69° as possible. 
(See international agreement, page 21, as to standard weight 
of sugar.) 

SUCROSE 

Under the term sucrose all forms of table sugar are included. 
The principal sources are: the sugar-cane, Saccharum ofjici- 
narum L.; beet. Beta vulgaris L.; sorghum. Sorghum sacchar- 
atum Persoon; sugar maple, Acer saccharinum L. In the 
crude state there is a noticeable difference, but so far as is 
known, the sucrose is identical in all cases. 

Adulterations are few. The addition of glucose, especially 
to the lower grades, formerly extensively practised, now rarely 
occurs. The difference in the grades depends largely upon the 
extent to which the molasses and mineral matter have been 
removed. Maple sugar is sold in the crude condition and is 
often adulterated. 

The usual examination of commercial sugar is determina- 
tion of the amount of water, ash, sucrose, and reducing sugar. 
Water and ash are determined, as on pages 27 and 39. In 
the best grades of sugar these will often not amount to more 
than 0.1 per cent. In the lower grades ash may be 3 per cent., 
and water between 10 and 15 per cent. The higher proportions 
of ash are found in beet-sugar. The estimation of sucrose is 
most conveniently made by the polarimeter. The direct read- 
ing is usually sufficient, but the result may be checked by 
hydrolysis, and reading at ordinary temperature and at 86°. 
The best grades will give a direct reading closely approximat- 
ing 100 per cent. In some cases the direct reading will slightly 
exceed 100, due to a small proportion of raffinose. The lower 
grades of sugar contain some invert-sugar, and the proportion 
12 



122 FOOD ANALYSIS 

of sucrose may be even below So })er cent. Maple sugar usually 
contains about 85 per cent, of sucrose. 

Coloring-matters. — Granulated and loaf sugars often con- 
tain ultramarine blue, added to improve color. It may be 
separated by dissolving a considerable quantity of the sample 
in water, allowing the coloring-matter to subside, and washing 
it with water several times by decantation. Ultramarine blue 
is decomposed by hydrochloric acid, the color discharged, 
and hydrogen sullid liberated. 

Tin chlorid is sometimes employed in order to give sugar 
a bright, lasting, yellow tint. The color appears to be the 
result of action on the sucrose. As a rule, the finished product 
contains but traces of tin, the greater portion being removed 
with the molasses. The so-called Demerara sugar is prepared 
in this way. Demerara sugar is frequently imitated by the 
addition of artificial coloring, usually to beet-sugar. To sepa- 
rate such added coloring-matter Cassel recommends the 
following method: 

About 100 grams of the sample are shaken with alcohol of 
90 per cent. This will often remove the color in a single 
washing. In some cases it is advisable to use alcohol of 75 
or 80 per cent. The solution is filtered from the sugar, evap- 
orated to dr}'ness, the color again taken up with alcohol, 
and a skein of silk or wool (preferably slightly mordanted 
with aluminum acetate) treated with the solution, warmed for 
some time, and subsequently well washed with water. The 
skein will be dyed of a more or less yellow color in the presence 
of artificial dye. A sample containing only such coloring- 
matter as is natural to sugar, even by repeated washing with 
alcohol of 90 per cent., does not leave absolutely colorless 
cr}stals, and does not give a solution capable of permanently 
dyeing silk or wool. It is probable that the wool test described 
on page 64 might be successfully applied to a solution in water. 
See also Crampton & Simon's test for caramel, page 125. 



SUGARS 123 

The occasional occurrence of artificial sweetening substances 
[e. g. saccharin, glucin) as substitutes for sugar in confections, 
fruit juices, jams, and similar articles must not be overlooked. 
The possibility of commercial glucose and invert-sugar con- 
taining arsenic and lead derived from the sulfuric acid must also 
be borne in mind. 

MOLASSES AND SIRUP 

Molasses is the uncrystallizable sirup produced in the 
manufacture of sugar. It properly differs from treacle in that 
it comes from sugar in the process of making, while treacle is 
obtained in the process of refining, but the two terms are often 
employed interchangeably. Treacle, often called refiner's 
molasses, may contain 35 per cent, or more of sucrose, which 
is prevented from crystallizing by the associated substances. 
Ordinary table-molasses is made from cane, sorghum, or 
maple. Molasses from raw cane-sugar contains considerable 
invert-sugar, from which beet-root molasses is comparatively 
free. The latter, however, contains raffinose and a great 
variety of other bodies; the proportion of salts being some- 
times 15 per cent. These impurities render it unfit for table 
use. Beet-sugar partially or wholly refined is free from these 
ingredients and may be used in the preparation of table sirups. 

Maple sirup is molasses from the maple. Some so-called 
maple sirup or "mapleine" is made by addition of extract of 
hickory-bark to sucrose or glucose sirup. 

Molasses and maple sirup are often adulterated by the addi- 
tion of glucose sirup. The product is usually sold as molasses, 
but is sometimes designated "mixed goods" or "table sirup." 
Glucose sirup produces a pale liquid, of good body, and many 
samples consist almost entirely of this material, flavored by 
the addition of a small proportion of the lowest grades of refuse 
molasses. 

The addition of glucose to molasses is readily detected by 



124 FOOD ANALYSIS 

means of the pokiriseope. The normal or half normal quantity 
for the instrument is prepared as described on page 119 and the 
reading taken. A portion of this solution is hydrolyzed, as 
described on page 118, and two readings taken, one at or near 
the same temi)erature as the direct reading, and a second at 86° 
(see page 17). Pure molasses generally gives on direct 
reading at a temperature of 20° a deviation corresponding to 
40 or 50 on the cane-sugar scale. After hydrolysis, the reading 
at the same temperature will be — 10 or — 20, and at a tempera- 
ture of 86° will be zero or near it. Sirups made by the solution 
of sucrose in water will usually give a rather higher direct 
reading, but after hydrolysis the results will be the same as with 
molasses. In the presence of any considerable quantity of 
glucose the direct reading is nearly always above 60 and may 
rise to 120 or more. After hydrolysis, the sample remains 
strongly dextrorotatory even at 86°. For determination of 
glucose see page 126. 

Dark molasses is often bleached. Bone-black is sometimes 
used, but ozone, hydrogen dioxid, sulfurous acid, sulfites, and 
sulfuric acid have been employed. One method consists 
in the addition of zinc dust and sodium sulfite, the zinc being 
subsequently removed by the addition of oxalic acid. The 
bleached molasses is liable, therefore, to contain either zinc 
or oxalic acid. 

As noted above, some samples of sugar are prepared by 
the use of stannous chlorid; the latter may pass into the mo- 
lasses in such proportion as to be dangerous. Copper is occa- 
sionally present, derived from the apparatus of the refinery. 
For the detection of metallic impurities in molasses, not less 
than 50 grams should be ashed and examined as described 
on page 40. 

The U. S. standard for molasses is not more than 25 per cent, 
of water nor more than 5 per cent, of ash. 

Caramel is a dark bro\Mi mass, soluble in water and weak 



SUGARS 125 

alcoholic liquids, obtained by heating sucrose to about 200°. 
It is largely used as a coloring- matter in foods and beverages. 
It is now occasionally adulterated or imitated by artificial 
coal-tar colors. The wool test will serve in many cases to 
detect these. Caramel as a coloring agent is most easily 
recognized by a method due to Crampton & Simons: The 
liquid is well shaken with a small quantity of fuller's earth 
and filtered. Coloring matters from charred or uncharred 
wood are not removed, but if caramel be present the filtrate will 
be noticeably paler than the original liquid. See also under 
"Alcoholic Beverages." 



GLUCOSE 

Commercial glucose consists principally of dextrose with 
considerable maltose and gallisin and some dextrin. In trade 
the term ''glucose" is restricted to the sirup; the solid is 
called "grape-sugar." Inferior qualities of glucose may con- 
tain sulfurous or sulfuric acid, calcium sulfate, arsenic, and 
lead. Glucose is often termed "corn sirup." 

The following are analyses of commercial glucoses; Nos. i 
and 2 are by Moritz & Morris, 3 and 4 by Stern. In Stern's 
analyses some figure has been determined by difference, prob- 
ably that given as " unfermentable bodies," in which the gallisin 
and nitrogenous matters are included. 

No. 1 No. 2. No. 3. No. 4- 

Dextrose, 50.58 47-71 7o-o ^>7-4 

Maltose, 

Dextrin, 

Gallisin, 

Nitrogenous matters, 

Unfermentable bodies, 

Ash, 

Water, 



14.19 


12.29 


5-1 


II.O 


1.76 


2.98 






15-59 


15.90 






1. 18 


0.81 










14.08 


4-3 


1.44 


1-39 


0.2 


1.6 


16.49 


20.77 


9.9 


157 


101.23 


101.85 


100. 


TOO.O 



126 FOOD ANALYSTS 

Lcaeh'' found thai the ^^lucosc coninionly used in adulterating 
molasses, maple siru[) and honey gives a direct reading of 87.5 
with a half-normal weight and 200 mm. tul)e, e(juivalent to a 
full reading of 175. He has, therefore, proposed to calculate 
the glucose on this basis, ])y the following formula: 

r- _ 100 (a — S) 

175 

This may be simplified to: 

= 0.561 (a — S) 

in which G is glucose, S, sucrose and a the polarimetric read- 
ing before hydrolysis. The amount of sucrose must be calcu- 
lated by the formula on page 120 from the reading before and 
after inversion. Some samples used for jellies and jams may 
show a reading as low as 150. If glucose of this quality is 
suspected, the constant in the above formula should be 0.666. 
The method therefore is approximative and suggestive. 

Freshly made solutions of dextrose show bi-rotation (as 
described under lactose). This disappears on standing at 
room temperature for 24 hours. It does not occur with sirups 
or the glucose used in adulterating sugar- or fruit-products, 
l)ut must be borne in mind in dealing with solid articles. 

The examination of glucose samples may be conducted as 
follows : 

Arsenic may be detected by Reinsch's test ; lead by the routine 
method given on page 58. The amount of free acid is deter- 
mined by titration of a known weight with standard alkali, 
using phenolphthalein as indicator. Sulfurous acid may be 
detected by adding some of the samples to dilute hydrochloric 
acid, with a few fragments of zinc in a test-tube, and covering 
the mouth of the tube with a piece of lilter-paper containing 
some lead acetate. A spot of lead sultid indicates reducible 
sulfur compounds. Calcium sulphate or other mineral matter 
may be determined ])y the weight and composition of the ash. 



SUGARS 127 

LACTOSE 

Commercial lactose is usually obtained from the whey of 
cows' milk. Inferior qualities contain notable amounts of 
nitrogenous matter, mineral substances, bacteria, and spores 
of fungi. Pure lactose is a white crystalline pow^der, not 
very soluble in water and feebly sweet. When crystallized by 
evaporation at low temperature, it retains one molecule of 
water, but this is easily removed. The freshly made solution 
in water has a dextrorotatory power much greater than normal; 
upon standing for 24 hours, or immediately upon boiling, it 
acquires its normal rotatory action. This phenomenon, 
known as "birotation," must not be overlooked in examining 
samples of lactose or concentrated milk-products. Lactose 
has high reducing power, especially upon alkaline copper 
solutions. Under the influence of some common organisms 
it is rapidly converted into lactic acid; by special methods it 
may be converted into ethyl alcohol. 

For qualitative tests for lactose see page in. Quantitative 
determinations are made either with a polarimeter or an 
alkaline copper solution. The details of these methods are 
given in connection with the analyses of milk. The examina- 
tion of commercial samples should be directed to the deter- 
mination of the amount of nitrogen, ash, lead, copper, and 
zinc. The sample should not be acid, nor contain any appre- 
ciable amount of matter insoluble in water. 

MAPLE SIRUP AND MAPLE SUGAR 

These are substantially sucrose with minute amounts of 
special flavors. Sucrose from other sources is often added. 
Adulteration with maple sirup glucose is also common. Much 
attention has been given to the standard composition of pure 
maple sugar, in order to determine adulteration with sucrose 
from other sources. 

Analytic mclhods. Glucose is detected by examination witli 



128 FOOD ANALYSIS 

the polarimclcr before and after hydrolysis. Pure maple 
sugar is inverted, glucose is but slightly affected. The follow- 
ing results ol)tained l)y Opjden illustrate this: 

Percentage 
polarimeter reading. sucrose. 

Direct. After Hydrolysis. 

Maple sirups free ( 53.1 — 22.2 56.0 

from glucose: ( 59.6 — 21.9 60.6 

^^ , ( 84.1 —28.8 85.9 

Maple sugars: | ^^ ^ _^g ^ ^^ ^ 

Maple sirups con- ( 80.0 18.9 

taining glucose :( loo.o 45.6 

The methyl alcohol method for detecting glucose in honey 
will be of some value. With pure maple sirup, the precipitate 
is abundant and fiocculent but not adherent to the glass. On 
standing, crystals of sucrose appear. When considerable 
glucose is present, a more granular precipitate appears which 
adheres to the glass. For determination of glucose, see page 126. 

The water in maple sirup is determined in the usual way, 
but it will be advantageous to use a dilute liquid and spread 
it over a large surface. Maple sirup should be diluted with its 
weight of water, and maple sugar dissolved in twice its weight 
of water. The drying should be completed in the water-oven. 

The most important data for judging of the' addition of 
sucrose are the amount and alkalinity of the ash, the amount of 
lead subacetate precipitate and the malic acid value. Frear,^^ 
who examined sirup and sugar made under his own observation, 
suggests a minimum relation of ash to sucrose of i to 160, that 
is, the ash should not be less than 0.625 of the total sucrose. 

The ash must be determined with care, as some of the consti- 
tuents are volatile. Burning in a muffle at as low a tempera- 
ture as possible is preferable. The weighing must be done 
promptly, as the ash is deliquescent. In some cases, the data of 
alkalinity of the water-soluble portion to phenolphthalein and 
methyl orange, and the alkalinity of the insoluble portion, will 
be needed as described on page 39. 



SUGARS 



129 



@ 



The lead subacetate precipitate is measured by volume after 
concentration by a centrifuge, according to the method of 
Hortvet.^^ A special tube and holder, shown in figure 37 on a 
scale of one-half, is used. Each tube must have a holder. 
Tubes and holders must be closely balanced in pairs, so that the 
centrifuge will be evenly loaded. The holder may be made of 
soft wood. Instrument-makers can, however, make aluminum 
holders that will be satisfactory. The narrow part of the tube 
should be graduated in c.c. and fractions. 

5 c.c. of sirup or 5 grams of sugar are placed in the tube, 10 
c.c. of water added, and the contents well-mixed, sugar being 
allowed to dissolve completely before the final 
mixing. 0.5 c.c. alumina cream and 1.5 c.c. --..| 

of lead subacetate (see page 118) are added, 
the mixture again shaken and allowed to 
stand for an hour, the tubes being occasion- 
ally rotated to facilitate settling. Tubes 
must, of course, be made up in pairs. They 
are placed in the centrifuge, run for about 
10,000 turns within six minutes, and exam- 
ined ; any material that may be adhering to 
the wider portion is loosened with wire at the 
end, the tubes again rotated for six minutes, 
and the volume of the precipitate noted, read- 
ing to o.oi c.c. if possible. Each operator must by trial with 
samples of definite origin establish standards applicable to the 
centrifuge used. Using an instrument with a radius of 18.5 cm., 
Hortvet obtained with pure maple sirups 1.2 to 2.5 c.c. and with 
pure maple sugars 1.8 to 4.0 c.c. Adulterated articles give much 
less. Experiments with pure sucrose and precipitants must 
be made and the volume of precipitate noted as a correction. 

The so-called "malic acid value," of use in judging the 
quaHty of maple products, is obtained by Hortvet's modifica- 
tion of the method of Leach & Lythgoe. 



Fig. 37. 



15 



1 30 FOOD ANALYSIS 

6.7 grams of ihc sam])lc arc weighed into a 200 c.c. beaker, 
water added lo make the volume 20 c.c, the solution made 
slightly alkaline with ammonium hydroxid, i c.c. of a 10 per 
cent, solution of calcium chlorid and then 60 c.c. of 95 per cent, 
alcohol added. The beaker is covered and heated for one hour 
on the water-bath, the heat withdrawn and the liquid allowed 
to stand overnight. The precipitate is collected by filtering 
through good filter paper (probably the hardened paper will 
be satisfactory), washed with hot 75 per cent, alcohol, until all 
calcium chlorid is removed, dried and ignited. 20 c.c. — 
hydrochloric acid are added, the solution warmed until the 
lime is dissolved and the excess of acid determined by titration. 
One-tenth the number of c.c. of acid neutralized is the provi- 
sional malic acid value. With pure maple products the figure 
will not be below 0.80. 



HONEY 

Honey consists principally of dextrose and levulose with 
small proportions of mineral and flavoring matters and often 
formic acid. In some cases small amounts of sucrose and 
mannitose and a considerable proportion of carbohydrates of 
the dextrin class are present. Microscopic examination will 
usually show pollen, portions of insects' wings, and spores of 
fungi. Crystallized dextrose is occasionally present. 

The color of honey varies from light amber-yellow to brown- 
ish-black, according to the source, and time and manner of 
storage. White clover honey is nearly colorless. Strained 
honey is that freed from comb by straining. Extracted honey 
is freed from comb by centrifugation or settling. 

The proportion of water ranges within the limits of 12 and 
22 per cent. The reducing bodies calculated as dextrose usu- 
ally amount to from 60 to 75 per cent. If sucrose be present 
in but small amount in the nectar of the flowers, it may be en- 



HONEY 131 

tirely hydrolyzed in the bee or after deposition in the hive, the 
honey being quite free. 

Honey contains no true dextrin, but many samples yield, 
with strong alcohol, precipitates of carbohydrate intermediate 
between starch and sugar, the proportion being as high as 40 
per cent, or more in the case of honey of coniferous origin. 

Dextrorotatory samples, apparently pure, have been reported. 
They were probably of coniferous origin. They have been 
disregarded in the official standard. 
U. S. Standard. 

Honey is the nectar and saccharine exudation of plants, 
gathered, modified and stored in the comb of the honey-bee 
{Apis mellifica). It is levorotatory. 

Water should not be over 25.0 

Ash should not be over 0.25 

Sucrose should not be over 8.0 

Adulterations. — Bees are often fed with cane-sugar, which 
they hydrolyze partially. Ogden gives the following results of 
polarimetric examination of honey obtained in this way : 

Direct, i8°-5- Temperature, 25.2°. 

After hydrolysis, — 9.0. Temperature, 24°. 

The common adulterants of strained honey are invert-sugar 
and glucose sirup. It is usually impossible to detect with 
certainty the addition of invert-sugar. An ash higher than 
0.3 per cent., containing a notable quantity of calcium sul- 
fate, may point to invert-sugar or to glucose sirup. Samples 
are frequently encountered which give a direct polarimetric 
reading of — 14 to — 20 on the cane-sugar scale, and, after 
inversion, slightly higher figures ; these in many cases probably 
contain added invert-sugar. 

The direct addition of sucrose to honey is not usual, but 
has been practised in some cases. Its presence in considerable 
quantity will be indicated by the high right-handed rotation, 



132 FOOD ANALYSIS 

decidedly reduced on hydrolysis. A sample of so-called " hoar- 
hound honey" examined in the chemical laborator)' of the 
U. S. Department of Agriculture was found to consist mainly 
of a solution of sucrose with some alcohol. 

A common method of adulteration consists in pouring 
glucose sirup over honeycomb from w^hich the honey has 
been drained, and allowing the mixture to stand until it has 
acquired a honey flavor. Such samples give a high positive 
polarimetric reading, but little affected by hydrolysis. 

Dextrin is a constant constituent of commercial glucose 
sirup, and the attempt has been made to detect the latter by 
the formation of a precipitate when the sample is diluted with 
alcohol. It has been shown, however, that many samples of 
honey contain a considerable material precipitable by ethyl 
alcohol, amounting in some instances to 50 per cent. Accord- 
ing to Beckmann, better results may be obtained by the use 
of methyl alcohol. Pure honey, both the ordinary form and 
the dextrorotatory variety, that might be regarded as adul- 
terated with glucose, was found to yield, when largely diluted 
with methyl alcohol, only a slight flocculent precipitate, which 
did not adhere to the walls of the vessel. Glucose sirup 
yielded a precipitate of dextrin amounting to about 31 per 
cent., which produced with a solution of iodin in potassium 
iodid the red characteristic of erythrodextrin. The reaction 
is also obtained by direct addition of the iodin solution to 
honey containing glucose sirup. The quantitative determina- 
tion is made by diluting 8 grams of the sample with 8 c.c. of 
water and diluting the mixture to 100 c.c. with methyl alcohol. 
The precipitate is filtered ofif, washed with methyl alcohol, 
dissolved in water, and the solution evaporated on the water- 
bath with repeated addition of methyl alcohol until quite dry. 
Adulteration with solid glucose (so-called grape-sugar) cannot 
be detected by this method, since in the preparation of this 
the hydrolysis is carried further. Methyl alcohol produces only 
a slight turbidity. 



HONEY 133 

Beckmann has also proposed the following test for solid 
glucose and glucose sirup: 5 c.c. of the honey solution (20 
grams in 100 c.c. of water) are mixed with 3 c.c. of a 2 per 
cent, solution of barium hydroxid, 17 c.c. of methyl alcohol 
added, and the mixture shaken. Pure honey remains clear, 
but in the presence of dextrin, glucose, or glucose sirup a 
considerable precipitate is formed. The test was applied 
quantitatively by increasing the amount taken to 50 grams, 
the methyl alcohol added rapidly to avoid deposition on the 
glass, the liquid well shaken once, the precipitate collected on 
a tared asbestos filter, washed with methyl alcohol and ether, 
and dried at 55° to 60°. Excessive shaking was avoided in 
order to prevent the action of air on precipitate. It was found 
that the quicker the working, the more accurate the results. 
In some cases it was found necessary to determine the sulfates 
and phosphates and to correct the results accordingly. The 
mean results in test analyses, calculated to i gram of the 
material taken, were: Dextrin, 0.916 gram; glucose sirup, 
0.455 gram; solid glucose, 0.158 gram. Admixture of dex- 
trorotatory conifer honey to the extent of 90 per cent, was not 
found to increase the amount of precipitate, but, on the con- 
trary, to diminish it slightly. 

The following are results obtained on samples of natural 
honey rich in dextrinous bodies. Sp. is the specific rotatory 
power for yellow light : 

Apple honey, Sp. = — 12.2. Precipitate by ethyl alcohol 23.7 per cent. 

Barium precipitate 5 c.c. 10 per cent, solution gave 0.0044 gram. 
" " 5 c.c. 20 per cent. " " 0.0072 " 

Umbellifer honey, . . . .Sp. = — 4.6. Precipitate by ethyl alcohol 29.1 per cent. 
Barium precipitate 5 c.c. 10 per cent, solution gave 0.0148 gram. 
" " 5 c.c. 20 per cent. " " 0-023 " 

Conifer honey, Sp. = 16.9. Precipitate by ethyl alcohol 41.9 per cent. 

Barium precipitate 5 c.c. 10 per cent, solution gave 0.0132 gram. 
" " 5 c.c. 20 per cent. " " 0.0248 " 

It appears from these data that even under unfavorable cir- 



134 FOOD ANALYSIS 

cumslanccs it i.s po.ssiblc to recognize the addition of from 5 
to 10 per cent, of ordinary dextrin, 10 to 20 per cent, of glucose 
sirup, and 30 to 40 per cent, of solid glucose to conifer contain- 
ing as much as 40 per cent, of natural dextrinous matter. With 
ordinary samples, such as the apple honey just noted, adultera- 
tion would ])e much more easily detected. 

For the determination of glucose Leach*® recommends hy- 
drolyzing in tlie usual manner, taking the reading at 87° (see 
page 17) and dividing by 175. The quotient is the approximate 
percentage of glucose. (See page 126.) 

Konig and Karsch have proposed the following method for 
detection of glucose: 40 grams of the sample are made up to 
40 c.c. with water, well mixed, 20 c.c. placed in a 250 c.c. flask, 
and absolute alcohol added, by very small portions at a time, 
with constant shaking, until the flask is filled to the mark. 
The mixture is allowed to stand for several days with occasional 
shaking. The solution is again shaken well and quickly 
filtered. 100 c.c. of the filtrate are evaporated to remove 
alcohol, but not to dryness, the residue made up to 20 c.c. by 
addition of lead subacetate and water, the solution filtered and 
examined in the polarimeter. 

The precipitate produced by alcohol is washed several 
times with 90 per cent, alcohol and then dissolved off the 
filter with water, evaporated on the water-bath, dried in the 
water-oven, and weighed. 

The following are some of the results obtained : 

Percentage of Reduc- 







Pol.arimetric Reading. 


iNG Carbohydrates 






Before Treatment .\fter Treatment 


Precipitated by 






with Alcohol. with Alcohol. 


Alcohol. 


Pure honey, 




.... -6.4 -8.5 


3-2 






—12.4 13.4 


1-7 






— 16.7 17.0 








—117 II. 7 


3-3 






—9.2 13.2 








—7.7 9.9 


9-7 






—9.9 12.5 








—7-5 6.2 


34.0 


Honey containing 


75 


per 




cent, glucose, 


. . . . 


.... 25.5 2.4 


20.6 



CANDIES AND CONFECTIONS 1 35 

Molasses is said to have been added to honey, but its use 
is infrequent. The ash of molasses is high and contains 
considerable chlorids. Beckmann suggests its detection by 
the production of a precipitate on addition of a solution of lead 
subacetate in methyl alcohol, the formation of which is at- 
tributed to the presence of rafhnose. 5 grams of the solution 
are mixed with 22.5 c.c. of methyl alcohol and 5 c.c. of a solu- 
tion of the honey (which should not contain more than 25 per 
cent.) are added. If the honey be pure, the solution will re- 
main clear, but in the presence of molasses a precipitate will be 
formed. The amount of precipitate varies according to the 
particular sample of molasses present, but Beckmann claims 
that it will usually be possible to detect as low as 10 per cent. 

CANDIES AND CONFECTIONS 

These terms include many articles, some complex mixtures, 
the composition of which is secret. The main ingredient is 
usually 'sucrose, but invert-sugar, dextrose, starch, mucilaginous 
substances, gelatin, colors, and flavors are largely employed. 
Among the objectionable ingredients are paraffin, clay, calcium 
sulfate, mineral colors, fusel oil, and metal foil. Preservatives 
are usually unnecessary. The use of mineral colors has declined 
much of late years, owing to the cheapness and superior brilli- 
ancy of artificial organic dyes, but some of the chocolate con- 
fections contain considerable amounts of brown ferric hydroxid. 

The plain candies, such as rock candy, molasses candy, and 
candy toys are usually only crystallized or melted sucrose 
with flavors and colors. Actual experiment by manufacturing 
confectioners has furnished the following data for proportion 
of color: 

One part of auramin will color 30,000 parts of melted sucrose 
to the deepest yellow required. One part of eosin or fluores- 
cein will give the average tint to 28,000 parts of ''cream goods" 
(such as used in high-class "mixtures") or 21,000 parts of 



136 FOOD ANALYSIS 

clear and hard candies, or 12,000 to 24,000 parts of s(^me other 
types. These figures are for "solid" coloring — that is, the 
whole mass is dyed; when merely surface-coloring is done, the 
quantity needed is about i part to 50,000. 

The ash of candies and confections is generally below one 
per cent. The flavors are often artificial. A brand called 
"Rock and Rye Drops" is often flavored with fusel oil. 

The colors employed are numerous and constantly chang- 
ing. At present various eosins (e. g., rhodamin B, rose bengale, 
erythrosin) are much used for red, fluorescein and auramin for 
yellow, malachite green and sulfonated alHes for green. Cochi- 
neal and vegetable colors, such as chlorophyl, cudbear and 
fustic, have come largely into use of late. Bismarck brown is 
apt to be employed in chocolate colors. 

Analytic Methods. — The examination of candies will be 
usually limited to identification of the coloring-matters and 
detection of starch, clay, calcium sulfate, paraffin, and poison- 
ous metals. Determinations of sucrose, invert-sugar, dextrose, 
and gum are difficult and of no practical interest. 

Glucose may be detected and approximately determined as 
in honey and maple sugar. 

A weighed portion of the sample is stirred in cold water 
until all soluble matter is taken up, the liquid is filtered in a 
Gooch crucible, the residue washed with cold water, trans- 
ferred to the crucible, dried at a low heat, weighed, burnt off, 
and again weighed. The figures for insoluble residue and 
ash will be obtained. The aqueous solution will usually 
contain the coloring and some of the flavoring material; the 
former may often be identified by the tests given on pages 64 to 
75. Many flavoring agents may be recognized by odor. If 
a moderately large sample is dissolved, fractional distillation as 
described in connection with fruit juices may give information. 
Starch may be detected by iodin. hny notable amount of 
gelatin or albumin will be indicated by the Kjeldahl method. 
Clay, calcium sulfate and iron oxid will be found in the ash. 



FATS AND OILS 137 

FATS AND OILS 

The methods for determining melting and soHdifying points 
and specific gravity of fats and oils have been fully described 
in the introductory part. Some comparative data are given 
in this section, together with methods applied almost exclu- 
sively to this class of food-products. 

Specific gravity determined at temperatures other than 
15.5° may be reduced to this by a correction of 0,00064 foi" 
each degree. This figure is derived from results obtained by 
Allen. The specific gravity of fats and oils changes by time. 
The following table, due to Thomson & Ballentyne, shows this 
fact ; the figures are for ^ 



15-5" 



15.5° * 






One Month. 


Three Months. 


Six Months 


0.9187 


0.9208 


0.9246 


0.9237 


0.9261 


0.9320 


0.9213 


0.9233 


0.9267 


0.9183 


0.9188 


0.9207 



Fresh. 

Olive, 0.9168 

Cottonseed, 0.9225 

Arachis, 0.9209 

Rape, 0.9168 

Color- tests. — Many color- tests for oils and fats have been 
proposed. The reactions are in some cases dependent on 
natural impurities and may fail when the sample has been pro- 
duced under unusual conditions or subjected to special treat- 
ment. Thus, cottonseed oil by heating loses susceptibility 
to several color-tests, while lard derived from animals fed 
liberally on cottonseed products will give distinctly the cotton- 
seed oil reactions. Special color-tests applicable to particular 
oils or fats will be described in connection with these. The 
following general reactions are much used : 

Sulfuric Acid Test. — ^A drop or two of strong sulfuric 
acid is placed in the center of about 20 drops of oil, allowed 
to rest a few moments, the color change noted, the mixture 
stirred, and the effect again noted. The charring action which 
often obscures the reaction may be avoided by dissolving a 
13 



138 



FOOD ANALYSIS 



drop of tlu' oil in jo drops of carbon disulfid and agitating 
this with the sulfuric arid. 

Nitric Acid Tkst. — Bach's method is to agitate 5 c.c. of 
the sample with 5 c.c. of nitric acid, sp. gr. 1.30. The color 
reaction is noted, the mixture immersed in boihng water for 
5 minutes, and the condition again noted. The reaction may 
be violent, and care must be taken to protect persons and 
apparatus against injury. 

Massie's method is to agitate 10 grams with 5 c.c. of nitric 
acid, sp. gr. 1.40, and note the color at the end of one hour. 

Lewkowitsch states that an acid of specific gravity 1.375 
is preferable. In some cases the mixture should stand 24 hours 
before the final observation is made. 

Mixtures of strong sulfuric acid and strong nitric acid have 
been used, but the results are not of material use with food oils. 

The following data, compiled by Allen, will illustrate the 
value of these color-tests : 





I 
Olive. 


Cotton- 
seed. 


Sesame. 


Arachis. 


Rape. 


Sulfuric Acid. — 












Before stirring, . 


Yellow- 


Red-brown. 




Yellow to 


Yellow 




green 






orange. 


with 




or brown. 








red rings. 


After stirring, . 


Brown or 


Dark red- 




Green or 


Brown. 




green. 


brown. 




brown. 




Nitric Acid. — 












Bach's test : 












After agitation 


Pale- 
green. 


Yellow- 
brown. 


White. 


Pale rose. 


Pale rose. 


After heating, 


Orange- 


Red-brown. 


Brown- 


Brown- 


Orange- 




yellow. 




yellow. 


yellow. 


yellow. 


After 12 hours' 












standing, . 


Solid. 


Buttery. 


Liquid. 


Solid. 


Solid. 


Massie's test, 


Yellow- 
green. 


Orange-red 


Yellow- 
orange. 


Pale red. 


Orange. 


Time for soliilifica- 












tion (minutes), 


j 60 


105 




105 


200 



FATS AND OILS 1 39 

lodin Number. — This, also called iodin value, is the per- 
centage of iodin absorbed under specified conditions. Baron 
Hlibl discovered that a solution of iodin and mercuric chlorid 
is more uniform in action than iodin alone, and this solution, 
commonly known as Hiibl's reagent, is usually employed. 
The following reagents are used in the process : 

Iodin solution. 25 grams of iodin are dissolved in 500 c.c. 
of 95 per cent, alcohol. 

Mercuric chlorid solution. 25 grams of mercuric chlorid 
solution are dissolved in 500 c.c. of 95 per cent, alcohol and 
the solution filtered, if necessary. 

Starch solution. See page 56. 

Potassium iodid solution. 15 grams in 100 c.c. of water. 

Potassium dichromate solution. 3.874 grams of pure potas- 
sium dichromate in 1000 c.c. of water. 

For use, equal parts of the iodin and mercuric chlorid solu- 
tions are mixed and allowed to stand at least 12 hours. 

The strength of the thiosulfate solution is determined as 
follows: 20 c.c. of potassium dichromate solution, 10 c.c. of 
potassium iodid solution, and 5 c.c. of strong hydrochloric acid 
are mixed in a glass-stoppered flask, and the solution of sodium 
thiosulfate is allowed to flow in from a buret until the yellow 
color of the mixture has almost disappeared. A few drops 
of starch solution are then put in and the addition of the thio- 
sulfate continued until the blue color just appears. The num- 
ber of cubic centimeters of thiosulfate solution used, multiplied 
by 5, is equivalent to i gram of iodin. 

Not more than i gram of fat is weighed in a glass-stoppered 
flask holding about 300 c.c, and 10 c.c. of chloroform or carbon 
tetrachlorid are added. After complete solution 30 c.c. of the 
iodin solution are added and the flask is placed in the dark for 
three hours, with occasional shaking. 20 c.c. of potassium 
iodid solution and 100 c.c. of water are added to the contents of 
the flask. Any iodin which may be noticed upon the slo]')per of 



I40 FOOD ANALYSIS 

the flask should be washed back into the flask with the potas- 
sium iodid solution. The excess of iodin is now titrated with 
the sodium thiosulfate solution, which is run in gradually, 
with constant shaking, until the yellow color of the solution 
has almost disappeared. A few drops of starch-paste are 
added, and the titration continued until the blue color has 
entirely disappeared. Toward the end of the reaction the 
flask should be closed and violently shaken, so that iodin 
remaining in the chloroform may be taken up by the potassium 
iodid solution. A sufficient quantity of sodium thiosulfate 
solution should be added to prevent a reappearance of any 
blue color in the flask for five minutes. 

At the time of adding the iodin solution to the fats, two 
flasks of the same size as those used for the determination 
should be employed for conducting the operation without fat. 
In ever}' other respect the performance of the blank experi- 
ments should be just as described. These blank experiments 
must be made each time the iodin solution is used. 

Iodin mofwbromid, used as suggested by Hanus,^^ is a satis- 
factor}' substitute for Hiibl's solution. It is prepared by dis- 
solving 13 grams of iodin in a liter of glacial acetic acid and 
adding 3 c.c. bromin, by which the halogen content is doubled. 
The acetic acid must be free from substances that reduce a 
mixture of chromic and sulfuric acids. The iodin mono- 
bromid keeps for several months and the maximum absorption 
occurs in 30 minutes, but oils of high iodin number should be 
given an hour. The solution is used similarly to that of Hiibl, 
except that an excess of at least 70 per cent, of unabsorbed 
iodin is necessar}', and only 10 c.c. of the potassium iodid solu- 
tion are added, the solutions being well mixed before the dilut- 
ing water is added. 

Especial care is needed in measuring the solution, as the co- 
efficient of expansion of acetic acid is high and sHght changes in 
temperature will cause appreciable errors. 



FATS AND OILS 



141 



loDiN Number or Liquid Acids. — This determination is 
sometimes of value for detection of admixture of vegetable 
oils with animal oils. The separation of the oleic and other 
liquid fatty acids is best made by the method of Muter & De 
Koningh, as follows : 

3 grams of the fat are mixed with 50 c.c. of alcohol and a 
fragment of potassium hydroxid in a flask furnished with a 
long tube. The mixture is boiled until saponi- 
fication is complete, when a drop of phenol- 
phthalein solution is added and acetic acid until 
the solution is slightly acid. Alcoholic solution 
of potassium hydroxid is added drop by drop 
until a faint permanent pink tint is obtained, 
when the liquid is poured slowly, with constant 
stirring, into a beaker containing a boiling solu- 
tion of 3 grams of neutral lead acetate in 200 c.c. 
of water. The solution is rapidly cooled and 
stirred at the same time, and, when cold, the 
clear liquid is poured off. The precipitate is 
well washed with boiling water by decantation, 
transferred to a stoppered bottle, mixed with 1 20 
c.c. of ether, and allowed to remain 12 hours. 
Wallenstein & Finck use a Drechsel gas- 
washing flask having the tube shortened about 
two-thirds, to contain the ethereal solution, and 
pass a current of hydrogen through it for about 
a minute. In the case of white fats the liquid is 
said to remain colorless at the end of 12 hours, but if free access 
of air is permitted, a dark-yellow solution is produced by oxida- 
tion. Lead oleate, hypogeate, linolate, or ricinolate will be dis- 
solved by the ether, leaving lead laurate, myristate, palmitate, 
stearate, and arachidate undissolved. Lead erucate is sparingly 
soluble in cold ether, but readily in hot. The contents of the 
bottle are filtered through a covered filter into a Muter separating- 




FlG. 38. 



142 FOOD ANALYSIS 

tube (Fig. 38), 40 c.c. of dilule hydrothloric acid (1:4) added, 
and tile lube slial^en until the elearin*^ of the etiiereal solution 
sliows that thr decomposition of the lead s()ai)s is comjjlete. The 
aqueous litiuid, containing lead chlorid and excess of hydro- 
chloric acid, is run off through the bottom tap, water added, 
and agitated with the ether and the process of washing by 
agitation repeated until the removal of the acid is complete. 
Water is then added to the zero mark and sufficient ether to 
bring the ether to a defmite volume (e. g., 200 c.c). An 
aliquot portion of this (e. g., 50 c.c.) is then removed through the 
side tap and the residue weighed after evaporation of the ether 
in a current of carbon dioxid. Another aliquot portion of the 
ethereal solution should be distilled to a small bulk (avoiding 
complete evaporation), alcohol added, and the solution titrated 
with decinormal sodium hydroxid and phenolphthalein or 
methyl-orange, from which the fatty acids may be calculated 
from the result, or their mean combining weight deduced there- 
from. A third aliquot part of the ethereal solution should be 
evaporated at about 60° in a flask traversed by a rapid stream 
of dry carbon dioxid. When every trace of ether is removed, 
50 c.c. of the iodin-mercuric chlorid solution (p. 139) should be 
added, the stopper inserted, and the liquid kept in absolute 
darkness for 12 hours, after which an excess of potassium iodid 
solution is added and 250 c.c. of water, and the excess of iodin 
ascertained with thiosulfate solution in the usual way. From 
the result the iodin number is calculated. The Hanus method 
may be used instead of the Hubl method. 

Volatile Acids. — This method was first suggested by Hehner 
& AngelV'^but was systematized by Reichert,^^and hence is gen- 
erally called the Reichert process. In this form it is carried 
out by saponifying 2.5 grams of the fat, adding excess of sulfuric 
acid, distilling a definite portion of the licjuid, and titrating the 
distillate with '^^- alkah. The number of cubic centimeters of 
this solution recjuired to overcome the acidity of the distillate 



FATS AND OILS 1 43 

is called the Reichert number. E. MeissP^ suggested the use of 5 
grams, and the number so obtained is called the Reichert- 
Meissl number. Alcoholic solution of potassium hydroxid was 
originally used for saponification, but the solution devised by 
Leffmann & Beam,^^ namely, sodium hydroxid in glycerol, is 
more satisfactory. The reagents and operation are as follows : 

Glycerol-soda. — 100 grams of pure sodium hydroxid are 
dissolved in 100 c.c. of distilled water and allowed to stand 
until clear. 20 c.c. of this solution are mixed with 180 c.c. 
of pure concentrated glycerol. The mixture can be conveni- 
ently kept in a capped bottle holding a 10 c.c. pipet, with a 
wide outlet. 

Sulfuric Acid. — 20 c.c. of pure concentrated sulfuric acid, 
made up with distilled water to 100 c.c. 

Sodium Hydroxid. — An approximately decinormal, accu- 
rately standardized, solution of sodium hydroxid. 

Indicator. — Solution of phenolphthalein or methyl- orange. 

A 300 c.c. flask is washed thoroughly, rinsed with alcohol and 
then with ether, and thoroughly dried by heating in the water- 
oven. After cooling, it is allowed to stand for about 15 minutes 
and weighed. (In ordinary operation this preparation of the 
flask may be omitted.) A pipet, graduated to 5.75 c.c, is 
heated to about 60° and filled to the mark with the well-mixed 
fat, which is then run into the flask. After standing for about 
1 5 minutes the flask and contents are weighed. 20 c.c. of the 
glycerol-soda are added and the flask heated over the Bunsen 
burner. The mixture may foam somewhat; this may be con- 
trolled, and the operation hastened by shaking the flask. When 
all the water has been driven off, the liquid will cease to boil, 
and if the heat and agitation be continued for a few moments, 
complete saponification will be effected, the mass becoming 
clear. The whole operation, exclusive of weighing the fat, 
requires about five minutes. The flask is withdrawn from the 
heat and the soap dissolved in 135 c.c. of water. The first 



144 



FOOD ANALYSIS 



portions of water should be added drop by drop, and the flask 
shaken between each addition in order to avoid foaming. 
When the soap is dissolved, 5 c.c. of the dilute sulfuric acid are 
added, a piece of pumice dropped in, and the liquid distilled 
until no c.c. have been collected. The condensing tube should 
be of glass, and the distillation conducted at such a rate that 
the above amount of distillate is collected in 30 minutes. 

The distillate is usually clear; if not, it should be thor- 
oughly mixed, filtered through a dry filter, and 100 c.c. of 




Fig. 39. 

the filtrate taken. A little of the indicator is added to the 
distillate, and the standard alkali run in from a buret until 
neutralization is attained. If only 100 c.c. of the distillate 
have been used for the titration, the number of cubic centi- 
meters of alkali should be increased by one-tenth. 

The distilling apparatus shown in figure 39 is that recom- 
mended by the A. O. A. C. (and since adopted in Great Britain), 
and the directions for preparing the flask are also from the 
same source, but when it is intended merely to distinguish 



FATS AND OILS I45 

butter from oleomargarin, it will be sufficient to measure into a 
flask 3 or 6 c.c. of the clear fat, and operate upon this directly 
in an ordinary distilling apparatus. 

A blank experiment should be made to determine the amount 
of standard alkali required by the materials employed. With 
a good quality of glycerol, this will not exceed 0.5 c.c. 

Most fats give distillates containing but little acid. 

Saponification Value. — ^Koettstorfer Number. — This is 
the number of milligrams of potassium hydroxid required for 
the saponification of i gram of fat. Its use was suggested 
by Berthelot, and it was applied to the examination of butter 
by Koettstorfer.^^ If the saponification value be divided by 10, 
the result will be the percentage of alkali required for saponi- 
fication. The reagents and process are as follows : 

Alcoholic potassium hydroxid. 40 grams of good potassium 
hydroxid are dissolved in sufficient alcohol to make 1000 
c.c. The solution should be clear and light yellow. Alcohol 
that becomes brown is unfit for use. 

Purified methyl alcohol and sodium hydroxid may be sub- 
stituted. The saponification value of sodium hydroxid may be 
converted into the standard number by multiplying by 1.4. 

Half-normal hydrochloric acid accurately standardized. 

Phenol phthalein solution. 

The process is as follows: About 1.5 grams of the sample 
are accurately weighed into a small flask, 25 c.c. of the alcoholic 
alkali added, and the mass saponified. The same amount of 
the alkaline solution must be used in all comparative experi- 
ments, and it must be accurately measured. The flask is 
provided with an inverted condenser or, more simply, with a 
tube about 50 cm. long and 0.5 cm. caliber passing through 
the cork. It is heated on the water-bath for 30 minutes, 
being occasionally given a rotatory motion. The alcohol 
should not boil actively. A drop of the indicator solution is 
added, the liquid allowed to cool somewhat, the flask being 
14 



146 



FOOD ANALYSIS 



closed, and then lilralcd with the standard acid. A Ijlank test 
should be made, which will eliminate some of the errors of 
experiment. The number of cubic centimeters used for titra- 
tion of the saponified mass, subtracted from the number used 
in the blank experiment, will give the acid corresponding to the 
alkali which has been neutralized by the fat. From this, the 
amount of alkali can be determined and calculated by simple 
proportion to i gram of fat. 

Flasks of the same kind of glass should be used in com- 
parative experiments, as some of the cheaper forms of glass 

are notably affected by alkali. A 
special form of saponification flask 
and method of heating used by the 
A. O. A. C. are shown in figure 40. 
The flask is arranged so that the 
cork can be tied down. 

x\llen suggested the use of the 
figure representing the grams of fat 
saponified by 1000 c.c. of normal 
alkali. This would render the 
method independent of the alkali 
employed, but the suggestion has 
not been generally followed. The 
PiQ ^Q datum was called by Allen saponi- 

fication equivalent. It may be ob- 
tained in any case 1j}' dividing 56100 by the saponification 
number. Similarly, the saponification number may be obtained 
by dividing 56100 Ijy the saponification equivalent. 

Acid Value. — This is the amount of free fatty acid. The 
reagents required are '^ sodium hydroxid and neutral alcohol. 
The latter is prepared by adding to a good quality of alcohol 
a dro]) or two of phenolphthalein solution and sodium hydroxid 
drop by drop with stirring until the color change occurs. 10 
grams of the sample are placed in a bottle provided with a glass 




FATS AND OILS 1 47 

Stopper, about 50 c.c. of the neutral alcohol and i c.c. of phenol- 
phthalein solution added, and the mass heated to boiling by 
immersing the bottle in hot water. The bottle is then stoppered 
and well agitated and the liquid titrated with standard alkali, 
the bottle being vigorously shaken after each addition until a 
faint pink coloration persists for a minute or two. On long 
standing the alkali acts upon the fat itself, i c.c. of — alkah is 
equivalent to 0.0256 gram of palmitic acid, 0.0284 gram of 
stearic acid, or 0.0282 gram of oleic acid. As the acid present 
may. not be known, it is usual to express the result as the 
milligrams of potassium hydroxid required to neutralize i gram 
of fat. This is called the acid number. When sodium hydroxid 
is used for titration, the acid number may be calculated by 
multiplying the quantity of sodium hydroxid required for i gram 
of sample by 1.4. 

Solubility in Acetic Acid. — Valenta's Test. — Fats and 
oils are arranged by Valenta into three classes, according to 
their solubility in acetic acid. Equal volumes of the oil and 
acid are placed in a test-tube, thoroughly mixed, and, if no 
solution takes place, warmed. 

Class I. — Completely soluble at ordinary temperature: 
Olive kernel oil ; castor oil. 

Class 2. — Completely soluble or nearly so at temperatures 
ranging from 23° up to the boiling-point of glacial acetic 
acid: Palm oil; coconut oil; olive oil; cacao-butter; sesame 
oil; cottonseed oil ; arachis oil; beef tallow; butter, etc. 

Class 3. — Not completely dissolved even at the boiling- 
point of glacial acetic acid: Oils obtained from the seeds of 
the Crucijer(E; rape-seed oil; mustard-seed oil; hedge-mustard 
oil. 

For the practical application of the test the method of Chatta- 
way, Pearmain, & Moor is satisfactory: 

2.75 grams of the sample are weighed in a short, rather 
thick tube with a well-fitting stopper, 3 c.c. of acetic acid 



148 FOOD ANALYSIS 

(99.5 per cent.) are added, the tube closed, placed in a beaker 
of warm water, and the heat increased until, after well shaking 
the tube, the contents become quite clear. The source of heat 
is then removed, and the test-tube so placed that it is in the 
center of the beaker of heated water, and, by means of a ther- 
mometer attached to the tube by a rubber band, the whole 
is allowed to rest until the change from brilliancy to turbidity 
takes place. The change is very definite, and can be repeated 
as often as is wished, with a maximum error of about 0.25°. 

Thermal Reaction with Sulfuric Acid. — Maumene's 
Test. — Maumene'"* found that on mixing sulfuric acid with 
drying oils a higher temperature is produced than with non- 
drying oils. With the same sample the temperature will 
depend upon the acid. The strength of acid employed should 
be determined by titration, since the specific gravity of the acid 
of 96 per cent, and of 99 per cent, is practically identical. L. 
Archbutt recommends the following method of operating: 
50 grams of the sample, weighed closely, are placed in a beaker 
of 200 c.c. capacity, and, together with the bottle of acid, placed 
in water until both have acquired its temperature, the thermom- 
eter having been placed in the oil. The beaker is removed, 
wiped, and placed in a nest of cardboard having hollow 
sides stuffed with cotton. (A beaker, lined with cotton, or, 
better, a vacuum jacketed test-tube, may also be used.) The 
temperature having been noted, 10 c.c. of acid are rapidly with- 
drawn from the bottle, which is immediately closed, the acid is 
allowed to flow into the oil while it is being stirred with the 
thermometer, and the stirring is continued until no further rise 
of temperature is observed. The stirring must be so managed 
as to effect as perfect admixture of the oil and acid as possible, 
thereby insuring an even development of heat throughout the 
mixture. 

The best results are obtained with an acid about 97 per 
cent. It is desirable to keep on hand a stock of oil of known 



FATS AND OILS 1 49 

purity, and to test some of this with each set of samples 
examined. 

Specific Temperature Reaction. — The discrepancies ob- 
served in Maumene's method may be largely eliminated by 
that devised by Thomson & Ballentyne,^^ which is to compare 
the rise of temperature with oil and with an equal volume of 
water under similar conditions. The number obtained by 
dividing the oil figure by the water figure is multiplied by 100 
to eliminate decimals, and the datum so obtained is called the 
specific temperature reaction. 

Bromin Thermal Value. — Hehner & MitchelP® ascertained 
that the heat evolved in the reaction of bromin vv^ith unsaturated 
fatty bodies furnishes more definite data than does sulfuric 
acid. As the action of bromin may be violent, it is moderated 
by a diluent such as chloroform, carbon tetrachlorid, or glacial 
acetic acid. The latter has the advantage, owing to its high 
boiling-point, of allowing a wider range of temperature. The 
procedure is as follows: The bromin, oil, and diluent are all 
brought to the same temperature, i gram of the oil is dissolved 
in 10 c.c. of chloroform in a vacuum-jacketed test-tube. Ex- 
actly I c.c. of bromin (measured by means of a pipet, connected 
at the upper end with a narrow tube filled with caustic lime, and 
having an asbestos plug at each end) is added and the rise of 
temperature determined by a thermometer graduated into 
fifths. Acids are dissolved in glacial acetic acid instead of 
chloroform. 

A definite relation exists between the iodin number and the 
heat produced by bromin. In Hehner & Mitchell's experi- 
ments it was found that if the rise of temperature in degrees 
was multiplied by 5.5, a close approximation to the iodin 
number was always obtained, except with rape and linseed 
oils, but each observer must ascertain the factor applying to 
particular cases. 

Wiley" has made this method more accurate and more easy 



150 FOOD ANALYSIS 

of application. A solution of bromin in four parts by volume 
of chloroform or carbon tetrachlorid is employed. This is to 
be made up in quantity sufficient for one day's use, and kept 
in the dark. Dissolving the sample in similar solvents is an 
additional convenience. 10 grams of the sample, in sufficient 
chloroform or carbon tetrachlorid to make 50 c.c. of solution, 
will suffice for nine determinations. At least four determina- 
tions should be made. The apparatus is shown in figure 41. 
The tube for holding the reagent and thermometer is about 
40 cm. in length, and 1.5 cm. internal diameter. It is conveni- 
ently held in a drying jar, being fitted air-tight by a rubber 
stopper. Air is withdrawn from the jacketing jar through the 
side tubulure. The bromin solution is contained in a stout- 
walled conical flask with a side tubulure provided with a rubber 
bulb. Through the stopper passes a pipet, and the flask may 
be rendered air-tight by gentle pressure on the stopper. The 
thermometer should be graduated to 0.2° and be read to a tenth 
by a lens. The operation should be conducted in a room at 
uniform temperature. 

The solutions and apparatus are allowed to stand until all 
reach a uniform temperature. 5 c.c. of the solution of the 
sample are placed in the inner tube by means of the pipet, 
without allowing any of the solution to run down the walls 
of the tube, the thermometer is inserted, and the bromin so- 
lution is forced up into the pipet by compressing the rubber 
bulb until the liquid has passed the mark on the stem. The 
top of the pipet is closed by the finger, the stopper of the flask 
loosened, and the liquid allowed to run out until it reaches 
the mark, when it is transferred to the mixing tube and allowed 
to flow directly into the solution of fat, but it is now not neces- 
sary to prevent the liquid running down the side of the tube. 
The empty pipet is returned to the flask and the thermometer 
is observed at once by means of a lens, since the bromination 
is practically instantaneous, the mercury reaching its maximum 



FATS AND OILS 



151 



height in about a minute after the pipet is withdrawn. When 
the mercury begins to fall, air is admitted to the jacketing 
space, the mixing tube is withdrawn, its contents emptied, and 




Fig. 41. 

the tube held inverted until the residual bromin vapor escapes. 
The tube may be cleaned by wiping it with a long test-tube 
cleaner or may be used again without cleaning, after standing 



152 FOOD ANALYSIS 

in\crte(l for half an hour. Traces of brominated oil which 
may remain upon the side of the tube do not interfere unless 
they obscure the thermometer. By the above manipulation 
the thermometer soon returns to the room temperature, and a 
second determination may be made in half an hour. 

As noted by Hehner & Mitchell, each analytic system must 
be separately standardized and the factor for calculating the 
iodin absorption determined. It is important not to stir or 
churn the mixture of oil and bromin further than is produced 
by the running in of the solution itself. Carbon tetrachlorid is 
the preferable solvent, but the rise of temperature is slightly 
higher with chloroform. 

Gill & Hatch"* have proposed to facilitate the comparison of 
tests made with different apparatus by employing a standard- 
izing material, and recommend sublimed camphor for this 
purpose. 7.5 grams of the camphor are dissolved in carbon 
tetrachlorid, the solution made up to 25 c.c, and portions of 
5 c.c. each brominated. The temperature increase obtained 
with various oils is divided by the rise observed with camphor, 
gi\ing a specific temperature increase, analogous to that sug- 
gested by Thomson & Ballantyne (see p. 149). By dividing 
the iodin value of an oil by the specific temperature increase, 
a figure will be obtained by which the iodin value may be ap- 
proximately calculated. 

Elaidin Test. — i c.c. of mercury is dissolved in 12 c.c. of 
cold nitric acid of 1.42 specific gravity. 2 c.c. of the freshly- 
made deep green solution are shaken in a wide-mouthed stop- 
pered bottle with 50 c.c. of the sample to be tested and the 
agitation repeated every ten minutes during two hours. When 
treated in this manner, oils consisting of nearly pure olein or 
of mixtures of olein with solid esters, such as palmitin and stearin, 
give more or less solid product. Olive oil is remarkable for the 
firmness of the canary or lemon-yellow mass formed. After 
24 hours the product is impervious to a glass rod, and some- 



FATS AND OILS 1 53 

times rings when struck; but this character is also possessed 
by the elaidins yielded by the arachis and lard oils. In making 
the- test, it is important to note the time required to. obtain a 
''solid" product, which will not move on shaking the bottle, 
as well as the final consistence. The temperature should be 
kept nearly constant, or erratic effects will occur. 

The behavior of the more important oils, when tested in the 
foregoing manner, is described by Allen as follows : 

A hard mass is yielded, among others, by olive, almond, 
lard, and sometimes arachis oils. 

A product of the consistency of butter is given by mustard, and 
sometimes by arachis and rape oils. 

A pasty or buttery mass which separates from a fluid portion 
is yielded by rape, sesame, cottonseed, sunflower, and some- 
times mustard oils. Liquid products are yielded by linseed, 
hempseed, walnut and other drying oils. 

The results of the elaiden test must be accepted with caution, 
since it is affected by many conditions, such as temperature, 
shape of the containing vessel, and the mode of preparation 
of the acid liquid. The extent to which the sample has been 
exposed to light and air is a still more important factor; it has 
been shown that olive oil after exposure to sunlight for two 
weeks may fail to respond to the test. 

Index of Refraction. — This datum differs notably in dif- 
ferent oils, but it is not of much value in detecting adulteration 
unless considerable of the adulterant be present. Several in- 
struments have been devised for making refraction determina- 
tion; the familiar ones are the refractometer of Abbe (figure 42) 
and the butyro-refractometer of Zeiss (figure 43). 

The butyro-refractometer has been strongly recommended 
for the examination of butter. It is equally adapted for the 
general examination of fats and oils, and may be used for the 
determination of the index of refraction as well. As these 
instruments are made by only one firm and are furnished with 
directions for use, further description will not be required. 



154 



FOOD ANALYSIS 



Drying Property. —Livache^s Test.-^ — The so-called drying 
of oils (a process of oxidation) is hastened by admixture with 
finely divided lead. This is prepared by precipitating lead 
acetate Ijv zinc, washing the precipitate rapidly with water, 
alcohol, and ether in succession, and drying at very low pres- 
sure. (Probably drying in nitrogen gas would be preferal)le.) 
I gram of tlie dried lead is mixed on a watch-glass with not 





Fig. 42. 



Fig. 43. 



more than 0.7 gram of the sample by dropping the latter so 
that it is distributed over the mass of the lead. The glass is 
allow^ed to stand at room temperature exposed to light, but 
reasonably protected from dust. 

Drying oils absorb the maximum quantity of oxygen after 
from 18 hours to 3 days, but non-drying oils do not begin to 
gain weight until after 4 or 5 days. Fat-acids, except those 



FATS AND OILS 155 

from cottonseed oil, behave the same as the fats. Livache's 
results are given in the following table. The figures show the 
percentage of increase in weight after the time specified. A 
drying oil (linseed) is added for comparison with the food oils. 
The figure for maize oil is given by Vulte & Gibson. 

Oil. 2 Days. 7 Days. 10 Days. 

Olive, o 1.7 

Cottonseed, 5 .9 

Maize, 5 .0 

Arachis, o 1.8 

Sesame, o 2.4 

Rape, o 2.9 

Linseed, 14.3 

Soluble and Insoluble Acids. — This method, due to Hehner 
& Angell,^^ has been much modified by other investigators. The 
proportion of acids insoluble in water is often called the Hehner 
value. The following method, described by Allen, is some- 
what different from that recommended by the A. O. A. C, but 
will serve for practical purposes, it being understood that blank 
tests and tests with standard oils should be made for comparison : 
About 5 grams of the sample, accurately weighed, are placed 
in a saponification flask, 50 c.c. of a solution of 40 grams of 
sodium hydroxid to 1000 c.c. of alcohol added, the flask closed, 
and the mixture heated in a steam-bath until complete saponi- 
fication has occurred. The flask is cooled, the soap solution 
acidulated with sulfuric acid, the aqueous liquid separated 
from the layer of fatty acids, and the latter several times boiled 
with a considerable quantity of water in a flask furnished with a 
reflux condenser. The liquids resulting from these operations 
are separated from the insoluble fatty acids, which it is desirable 
to boil again with a moderate quantity of water, while driving 
a current of steam through the flask in which they are con- 
tained, collecting the distillate, and treating it like the wash- 
ings. The acidulated aqueous liquid first separated from the 



15^ FOOD ANALYSTS 

layer of fatty acids is then distilled to a small bulk, and the dis- 
tillate exactly neutralized with standard sodium hydroxid, using 
phenolphthalein as an indicator. The lirst washings from the 
insoluble fatty acids are then added to the contents of the dis- 
tilling flask, and tlie liquid again distilled to a small bulk, the 
process being repeated with the succeeding washings. The 
different distillates should be titrated separately with decinor- 
mal alkali and phenolphthalein, so that the progress and com- 
pletion of the washing may be followed, and some information 
obtained as to the nature and relative proportions of the lower 
jatty acids present. 

The neutralized distillates should be united and evaporated 
gently to dryness, and the residue dried at ioo° until the weight 
is constant. It consists of the sodium salts of the acids that 
passed over in the distillation. If the number of cubic cen- 
timeters of -~- sodium hvdroxid emploved for neutralization 

lO •/ I ' 

be multiplied by 0.22, and the product be subtracted from the 
weight of the dry residue, the difference will be weight of the 
volatile acids. 

When coconut oil and palmnut oil are treated in this man- 
ner, the distillate will be found to contain lauric acid, which, 
though almost insoluble in water, is volatile in a current of 
steam. It may be separated from the more soluble volatile 
fatty acids by filtering the distillate. 

Acetyl Value. — This determination, originally suggested 
by Benedikt, is most conveniently carried out by the method 
of Lewkowitsch^^ : 10 grams of the sample are boiled for two 
hours with an equal volume of acetic anhydrid in a flask pro- 
vided with an inverted condenser; the mass is then transferred 
to a larger beaker, diluted with several hundred cubic centi- 
meters of water, and boiled for 30 minutes, with a slow current 
of carbon dioxid passed through by means of a tube drawn out 
to a fine opening at the lower end. This prevents bumping. 
On cooling, two layers are formed. The water-layer is drawn 



FATS AND OILS 1 57 

off by a siphon and the other portion washed three times by 
boihng with convenient measures of water. Prolonged wash- 
ing should be avoided. The acetylated product is freed from 
water by filtration through a dry filter in a water-oven at 100°. 

5 grams of the substance are saponified as noted on page 
145, the alcohol is evaporated, and the soap dissolved in water. 
The subsequent operations may now be completed by two 
methods, "distillation" or "filtration." The latter is the 
shorter and more convenient. 

Distillation Method. — The liquid is made up to a volume of 
several hundred cubic centimeters in a flask fitted with an 
arrangement for passing in steam or for adding water from 
time to time. Sufficient dilute sulfuric acid (i part of acid to 
10 of water) is added to make the liquid slightly acid, and dis- 
tillation is carried on until about 700 c.c. are collected. The 
distillate is filtered and titrated with decinormal alkali. Phe- 
nolphthalein is recommended as an indicator, but probably 
methyl-orange will serve as well. The number of cubic cen- 
timeters of solution required to neutralize the distillate, mul- 
tiplied by 5.61 and the product divided by the weight of the 
acetylated material, gives the acetyl number. 

Filtration Method. — The solution of the saponified acetyl- 
ated substance is mixed with sufficient standard sulfuric acid 
to be equivalent to the alkali added for saponification, and the 
mixture warmed gently. The acids will separate as an oily 
layer. The layer is removed, washed with boiling water until 
the washings are not acid, titrated with decinormal alkali, and 
the acetyl number calculated as above. 

The acetyl number is the number of milligrams of potas- 
sium hydroxid required for neutralizing the acetic acid ob- 
tained from I gram of the acetylated substance. 

In this process cholesterol and phytosterol are included in 
the acetylization. 

Substances yielding volatile acids give an acetyl number 



158 



FOOD ANALYSIS 



too high; tliis coiKhlion will affect the distillation method more 
than the filtration method. To eliminate most of this error, 
the percentage of volatile acid should be determined and the 
figures obtained deducted from the acetyl number. 

The water used in both methods should be freed as far as 
possible from carbon dioxid. Even the water used in pro- 
ducing the open steam should be brought to active boiling be- 
fore the steam is let into the flask. Waters rich in carbonate 
are especially objectionable. A slight excess of sulfuric acid 

causes the insoluble acids to separate 
better, but this must, of course, be 
know^n accurately and allow^ance made 
for it. 

It is possible that the data elucidated 
by Richmond with regard to the rate 
of distillation of acids of the acetic 
series could be applied to the distilla- 
tion method with advantage, but a 
special investigation will be needed to 
determine the point. 

Viscosity . — Practical determina- 
tions of viscosity are comparative only 
and are of little value unless uniform 
methods are employed. Many forms 
of viscosimeter have been devised. 
They are of two types, resistance and 
flow instruments. In tlie former, the viscosity is measured by 
the resistance to the movement of an immersed solid; in the 
latter, the time required for tlie flow of a given volume of 
liquid is measured. DooHttle's torsion viscosimeter is the best 
of its class; Reilly's (figure 44) is the best of the second class. 
Descriptions of these instruments and of methods of operation 
are unnecessary, as they are made according to standard 
patterns and full working directions are furnished with them. 




Fig. 44. 



FATS AND OILS 1 59 

Blasdale^^ investigated the relative viscosities of solutions of 
soap from different grades of olive oils and found the figures 
of much value. He used the torsion viscosimeter. The prepa- 
ration of the solution is as follows: 15 grams of the sample 
are saponified with a mixture of 10 c.c. of alcohol and 30 ex. 
of water containing 7.5 grams of potassium hydroxid. The 
mass is washed into a large dish, heated until the alcohol is re- 
moved, diluted to 500 c.c. at 20°, and the viscosity determined. 
The result is expressed by Blasdale in the number of grams of 
sugar that it would be necessary to add to a liter of water to get 
the same readings. With some oils it would be necessary to 
dilute the solution to 1000 c.c. 

Blasdale's results were as follows: 

Oils. Viscosity. 

Olive (California), 573~655 

Cottonseed, 280 

Aractiis, 220 

Sesame, 415 

Rape, 670 

Sweet almond, 645 

Mustard-seed oils give high viscosity figures, and a mixture 
of these with cottonseed oil in some proportions would escape 
detection by this test. 

Unsaponifiable Matter. — Most fats and oils contain un- 
saponifiable matters, the extraction and examination of which 
are useful data. The operation is most conveniently performed 
by saponifying with a solution of sodium (or potassium) hy- 
droxid in alcohol, evaporating the alcohol, dissolving in water, 
and extracting this solution with ether. The extraction of 
the dry soap with ether is not so satisfactory. The use of the 
watery solution is due to Allen. The operation is most con- 
veniently carried out in a stoppered separator. 

Separation does not always occur readily, but may often be 
induced by cooling the contents by adding a little sodium hy- 



l6o FOOD ANALYSIS 

droxid solution, more ether, or a few cubic centimeters of alcohol 
and rotating the mass gently. The aqueous liquid is run out, a 
few drops of sodium hydroxid solution and lo c.c. of w^ater are 
added, gently agitated, and run off. This treatment is repeated, 
after which the ether is run off in a tared flask, the aqueous 
liquid is agitated with a fresh portion of ether, which is washed 
and poured into the tared vessel as before. This process is 
again performed, when it will be complete. The ethereal solu- 
tion may be fluorescent if petroleum products are present. 
The greater portion of the ether should be distilled off in a 
recovering apparatus and the rest evaporated in the water bath. 
If the mass retains globules of water, the flask should be held 
horizontally and rotated rapidly so as to spread the residue in 
a thin layer. When no more water is visible and the odor of 
ether is very slight, the flask is placed on its side in the water- 
oven for 15 minutes, cooled, and weighed. 

Long heating should be avoided, as some hydrocarbons are 
sensibly volatile at 100°. Spermaceti and waxes yield in this 
process a large percentage of unsaponifiable matter, hence it 
is not available for the detection of paraffin in such substances. 

In ordinary cases the distribution of the bodies will be as fol- 
lows, but some resins will pass into the water in the form of 
sodium salts : 

In the Ether: In the Water: 

Hydrocarbons. Sodium salts. 

Mineral oils. Glycerol. 

ParaflQn. Sodium hydroxid. 

Neutral resins. 

Coloring-matters from palm oil. 
Cholesterol and analogs. 

Cholesterol and Analogs. — In the examination of commer- 
cial edible oils, the cholesterols are the most important of the 
above ingredients. Cholesterol is a member of a series of alco- 
hols, having physical characters somewhat like those of fats. 
There are a number of homologs, but the individual members 



FATS AND OILS l6l 

of the group with a few exceptions have been but Httle studied. 
Cholesterol occurs abundantly in some animal fats, such as 
wool-grease, and has been supposed to be present in olive oil as 
an exception among vegetable oils, but the investigations of Gill 
& Tufts ^^ have made this doubtful. Vegetable oils contain anal- 
ogous bodies. Among the most common of these is phy to sterol. 
Some cereals contain a homolog termed sitosterol, and oils from 
these seeds will be liable to contain it. 

A general method for the extraction of these substances is 
that of Foster & Riechelmann: 50 grams of the fat are twice 
boiled, for about 30 minutes at a time, with 75 c.c. of alcohol in 
a flask fitted with an inverted condenser, the flask being mean- 
while well shaken. The alcoholic solution is mixed with 15 
c.c. of 30 per cent, sodium hydroxid solution, and boiled on 
the water-bath in a flask fitted with a condensation tube until 
about one-fourth of the alcohol is evaporated. The fluid is 
then evaporated nearly to dryness in a porcelain basin and the 
residue shaken with ether. The ethereal solution is evaporated 
to dryness, the residue dissolved in about 40 c.c. of water, 
shaken out with a mixture of 75 c.c. of ether and 3 c.c. of alcohol, 
the solvent removed, washed three times with water, evaporated, 
and the residue crystallized from alcohol. 

Von Raumer determines the amount of crude cholesterol as 
follows: 50 grams of the oil are saponified with alcoholic po- 
tassium hydroxid. The resulting soap is evaporated to dryness, 
reduced to powder, and extracted with 50 to 75 c.c. of ether in 
a Soxhlet apparatus, plugs of fat-free cotton being placed above 
and below the layer of soap. The residue is saponified again 
with 10 c.c. of half normal alkali evaporated to dryness with 
sand, and re-extracted as before during two hours. When 
the work is carefully done, the second saponification and ex- 
traction is unnecessary. 

The following amounts of residue calculated to 100 grams 
of sample were obtained by this method: Cottonseed oil, 0.719 
15 



l62 



FOOD ANALYSIS 



gram; sesame oil, 1.314 grams lo 1.325 grams; lard, 0.217 



gram. 



These substances arc insoluble in water, sparingly soluble 
in cold alcohol, freely in boiling alcohol, and in the other com- 
mon solvents immiscible with water such as ether, chloroform, 
petroleum spirit. They are distinguished from each other by 
melting-point, crystalline form and some color reactions as fol- 
lows : 





Cholesterol. 


Phytosterol. 


Sitosterol. 


Melting-point. 


145° 


132-4° 


137-8° 


Crystals from hot 


Rhombic plates, 


Needles, 


Narrow plates, 


alcoholic solu- 


often with re- 


grouped i n 


with pointed 


tion. 


entering angles. 


tufts. 


terminals. 


Solution in 


Bluish green 




Clear green 


dilute acetic 


becoming 




changing to 


anhydrid with 


reddish yellow. 




pure yellow. 


sulfuric acid. 








Solution in 


Blood red. 


Blood red 


Blood red 


chloroform 




becoming 


becoming 


with sulphuric 




cherry red. 


purple. 


acid. 









The color reactions are obtained by dissolving a little of the 
sample in a few c.c. of the solvent, adding strong sulfuric acid, 
shaking, and allowing the liquid to stand for some time. The 
results are somewhat vague and it is not impossible that a por- 
tion of the action is due to unknown impurities. According to 
Salkowski, cholesterol gives with chloroform and sulfuric acid 
the following effects: The solution immediately becomes 
blood red, afterward cherry red and purple; the last lint re- 
mains for several days. The sulfuric acid layer under the 
chloroform shows a strong green fluorescence. On pouring a 
few drops of the purple chloroform layer into a porcelain basin, 
the red color changes rapidly to blue, green, and finally to yellow. 
On diluting the purple chloroform solution with more chloro- 
form, it becomes nearly colorless, or acquires an intense blue; 



FATS AND OILS 1 63 

if it now be shaken again with the sulfuric acid layer, the former 
coloration appears. These latter changes of color are due to 
traces of water in the chloroform. 

The solution of phytosterol gives the same reaction with 
sulfuric acid, but there is the slight difference that the coloration 
obtained with the former passes after a few days into a bluish- 
red, whereas the cholesterol solution remains more of a cherry 
red. In the crystallization from alcohol, if a mixture of chole- 
sterol and phytosterol is present, the crystals show one form 
either approximating to that of phytosterol or, if cholesterol is 
present in the greater quantity, differing from the pure crystals 
of either body. 

Analytic Data. — The data, commonly termed "con- 
stants," obtained by the processes described in the preceding 
pages, are subject to uncertainty, owing to the want of abso- 
lute standards. Fats and oils, being mixtures of several in- 
gredients, will vary with conditions of growth of the animals 
or plants yielding them, methods of extracting and refining, 
exposure to light, heat, and air, and, doubtless, from unrecog- 
nized causes. Samples prepared in the laboratory do not 
necessarily serve as standards for commercial products. Er- 
rors of observation from defective apparatus, especially in- 
accurate thermometers, are by no means uncommon. 

The data for specific gravity and for melting and solidifying 
points given in the following tables have been compiled from 
the best accessible sources, and will give a general idea of the 
range of figures in commercial samples: 



164 FOOD ANALYSIS 

SPKdllC (IkAVITIKS OF FATS, OILS AND FATTY ACIDS. 

Oils. Acids. 

(15.5°.) (ioo°.) (ioo°.) 

Olive, 0.914-0.918 0875 

Cottonseed, 0.922-0.925 0.8725 0.882 

Maize, 0.922-925 0.8711 

Coconut, 0.912 0.868-0.874 0.844 

Arachis, 0.916-0.922 0.847 

Sesame, 0.922-0.924 

Rape, 0.913-0.917 0.875-0.879 

Cacao-butter, 0.948-0.976 0.85 7 

Lard, 0.932-0.938 0.859-0.864 0.837-0.840 

Tallow, 0.893-0.898 0.870 

Butter-fat, 0.926-0.940 0.909-0.914 

Coconut olein, 0.926 0.907 

lODIN NUMBERS OF FATTY ACIDS. 
Oil or Fat. Mixed Acids. Liquid Acids. 

OKve, 86-90 

Cottonseed, 11 i-i 1 6 147 

Maize, 1 13-1 25 140 

Arachis, 95-103 128 

Sesame, 109-1 1 2 

Rape, 99-105 

Coconut, 8.5-9 54 

Cacao-butter, 32-5-39 

Butter-fat, 28-31 

Lard, 64-81 104 

MELTING AND SOLIDIFYING POINTS AND TITER-TESTS. 
The titer-tests were determined by Lewkowdtsch. 

Oil or Fat. Acids. 

Melting. Solidifying. Melting point. Titer-test. 

Olive, 4 to — 2 241027 16.9 to 26.4 

Cottonseed, i to 10 35 to 40 32.2 to 37.6 

Maize, not above — 10 18 to 20 

Coconut, 20 to 28 14 to 23 24 to 27 21.2 to 25.2 

Arachis, — 5 281033 28.1 to 29.2 

Sesame, — 4 to — 6 231031 21.21023.8 

Rape, — 6 to — 10 18 to 22 11.71013.6 

Cacao-butter, 30 to 34 20 to 27 48 to 52 48.0 to 48.2 

Lard, 281045 27 to 44 35 to 47 41.4 to 42.0 

Butter-fat, 29 to 35 20 to 30 36 to 46 (insol.) 

Beef tallow, 361049 33 to 48 431047 37.91046.2 

Mutton tallow, 36 to 49 33 to 48 46 to 54 40. i to 48.3 



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165 



1 66 FOOD ANALYSIS 

Special Tests. — Several tests are of value for recognizing 
particular oils or fats. The indiciitions for their use will be 
given in connection with these. 

Carbon disulfid-suljur test. — llalphcn^s test. — -This is in- 
tended for the recognition of cottonseed oil. It is applicable 
both to oils and mixed acids. 

Carbon disullid containing about i per cent, of sulfur in 
solution is mixed with an equal volume of fusel oil. Equal 
volumes of this reagent and the sample (about 3 c.c. of each) 
are mixed and heated in a bath of boiling brine for 15 min- 
utes. If no red or orange tint is produced, i c.c. of the re- 
agent is added, and if after 5 or 10 minutes more heating no 
color is shown, a third addition of i c.c. may be made. It is 
possible to detect very small quantities of cottonseed oil by 
this test. Lard and lard oil derived from animals fed on cot- 
tonseed meal will often give a faint reaction. 

Silver nitrate test. — BechPs test. — This is a test for cotton- 
seed oil. Several modifications are in use. According to Del 
Torre, the following reagents are required : 

A 

Silver nitrate, i .o gram. 

Alcohol, 200.0 c.c. 

Ether, 40.0 c.c. 

Nitric acid, o.i gram. 

B 

Fusel oil, 1 00.0 c.c. 

Rapeseed oil, 15.0 c.c. 

10 C.C. of the oil to be examined are mixed in a test-tube 
with I c.c. of reagent A, and then shaken with lo c.c. of 
reagent B. The mixture is next divided into two equal por- 
tions, one of W'hich is immersed in boiling w^ater for 15 
minutes. The heated sample is then removed from the water- 
bath, and its color compared with the unheated half. Cotton- 
seed oil is indicated by the reddish-brown of the heated portion. 



FATS AND OILS 167 

Only the purest alcohol should be used, and the rapeseed oil 
used should be "cold drawn," and only slightly colored; it 
should be filtered in a hot- water oven before preparing the re- 
agent. To guard against errors from impurity of the reagents, 
a blank test should be made. 

It is stated that old and rancid samples will not react unless 
the rape oil be present. Most chemists, however, do not use 
it, especially in testing lard. Hehner uses reagent A, add- 
ing I volume to 2 volumes of oil and heating for 15 minutes. 
Milliau uses A with the mixed fatty acids; but experience has 
shown that in some cases, in which cottonseed oil was present 
and responded to the test, the fatty acids failed to give a similar 
reaction. After heating to 240° or on long keeping, both oil 
and fatty acids may fail to respond to the test. 

Furfural test. — Badouin^s test. — This is a test for sesame 
oil. In its original form, the sample was shaken with a mix- 
ture of sucrose and strong hydrochloric acid, when a crimson 
is produced if sesame oil be present. As furfural is a prod- 
uct of the action of hydrochloric acid on sucrose, and is the 
active agent in the test, Villavecchia & Fabris have substi- 
tuted an alcoholic solution of the latter for the sugar. The 
solution is made dilute (2 per cent.), as furfural itself gives a 
violet tint with hydrochloric acid. The modified test is ap- 
plied in one of the following forms : 

(a) 0.1 c.c. of the 2 per cent, furfural solution is placed in 
a test-tube, 10 c.c. of the sample and 10 c.c. of hydrochloric 
acid (sp. gr. 1.19) added, the mixture shaken for half a min- 
ute, and allowed to settle. In the presence of even less than 
I per cent, of sesame oil, the aqueous layer will become crimson. 
In the absence of sesame oil the lower layer is either colorless 
or, at most, becomes, as in the case of very rancid though pure 
olive oil, dirty yellow. 

(b) 0.1 c.c. of the furfural solution is mixed with 10 c.c. of 
the sample and i c.c. only of hydrochloric acid added; the 



1 68 FOOD ANALYSIS 

mass shaken thoroughly and separation brought about by 
addition of lo c.c. of chloroform, or by a centrifuge, when 
the aqueous layer will be crimson with even less than i per 
cent, of sesame oil. 

Pyrogallol test (Tocher^ s test). — i gram of pyrogallol is dis- 
solved in 15 c.c. of hydrochloric acid and shaken with an 
equal volume of the sample. After separation, the watery 
liquid is boiled. Sesame oil produces a solution that is red by 
transmitted, and blue by reflected, light. 

Brulle^s test, o.i gram of finely powdered egg albumin and 2 
c.c. of dilute nitric acid (3 c.c. of nitric acid and i c.c. of 
water) are mixed with 10 c.c. of the sample, the mixture heated 
in a test-tube, without stirring, to boiling, and then shaken 
cautiously until the albumin dissolves. Care must be taken 
in this as the action may be violent. Cottonseed, arachis, 
rape and sunflower oils give red solutions; olive oil and lard 
yield an elaidin but no color. 

OLIVE OIL 

Olive oil is obtained from the fruit of the Olea europcea L. 
Its color usually ranges from light yellow to golden yellow, but 
some forms are deep green from presence of chlorophyl. The 
quality of the oil depends on many conditions; that intended 
for food is always expressed cold. 

Olive oil contains about 28 per cent, of solid fat, consisting 
of palmitin and a little arachidin. The remainder is mostly 
olein, with a little linolin. Hehner & Mitchell found no stearin. 
Appreciable amounts of cholesterol are present, differing from 
most vegetable oils, which contain phytosterol. The un- 
saponiliable matter ranges from i to 1.5 per cent. Free fatty 
acid is always present, amounting in the best grades to about 
1.5 per cent., and in the lowest grades to 25 per cent. 

Adulteration. — Olive oil is very liable to adulteration. In 
this country, cottonseed oil and arachis oil are the additions 



OLIVE OIL 169 

most commonly employed. In many cases the article con- 
tains no olive oil, cottonseed oil or a mixture of cottonseed 
and arachis oil being substituted. Other adulterants are 
sesame, rape, poppyseed, and lard oil. Still more rarely, 
curcas oil, and even castor oil have been employed. It is 
stated that 15 or 20 per cent, of the latter may be present with- 
out affecting the taste. In the lower grades of oil, not intended 
for table use, any ordinary oil, including refined petroleum, 
may be present. 

Specific Gravity. — The specific gravity of olive oil usually 
ranges from 0.914 to 0.917, or even 0.918 in the case of Cali- 
fornia oils. Commercial, usually brown, oils, expressed at 
a high temperature, and containing a higher proportion of 
palmitin, may range as high as 0.925. A specific gravity of 
0.918 or over, in a sample of light color, would give rise to 
suspicion of adulteration with cottonseed, poppyseed, or se- 
same oil. 

Solidifying- point. — Olive oil has usually a higher solidifying- 
point than any other of the vegetable oils. Mixtures of olive 
with other oils have, as a rule, a lower melting-point than either 
constituent alone. The melting and solidifying points of the 
mixed acids are also of some value, but, according to Dieterich, 
less than 25 per cent, of adulteration cannot be detected with 
certainty. 

Saponification Value. — This determination is of use only in 
the case of adulteration with a considerable proportion of rape 
oil. 

lodin Number. — This determination furnishes the most 
valuable indications of the purity of olive oil. The figure for 
pure oil usually ranges between 81.5 and 85 per cent. Values 
as high as 88.6 have been reported from some California oils, 
but such samples are exceptional, and a figure above 85 should 
give rise to suspicion of adulteration. 

Heat oj Bromination. — Specific Temperature Reaction. — The 
16 



lyo FOOD ANALYSIS 

thermal values of olive oil are lower than those of other vege- 
table oils and the determination is frequently of use. 

Elaidin Test. — Olive oil yields the hardest elaidin of all the 
oils, and in the shortest time, but, as noted on page 153, too 
much reliance must not be placed upon the indications of 
this test. The following figures, obtained by Blasdale from 
fresh California oils, of known purity, serve to show that the 
times required to form a solid product may differ much: 

Time Required for 
Brand of Oil. Elaidin Test. 

Uvaria, 6 hours. 

Pendulina, 4 " 

Redding Pccholinc, 3 " 

Ncvadillo bianco, 2 " 

Manzanillo, 30 minutes. 

Rcjractive Poiver. — The refractive power of olive oil is less 
than that of any other of the vegetable oils. The determination 
of the refractive index gives reliable indications only in the 
presence of a considerable proportion of the adulterant. The 
most satisfactory results are obtained by the butyrorefracto- 
meter. (See table on page 165.) 

Nitric acid test. — This will detect small amounts of cotton- 
seed oil in olive oil. Some operators employ acid of 1.41 spe- 
cific gravity, but, according to Lewkowitsch,^'* one of 1.375 gives 
better results. He recommends that the mixture be allowed to 
stand about 24 hours, when olive oil containing cottonseed oil 
becomes pure brown; but if rape oil be present, the mixture 
becomes more yellowish. Attention has been called to the fact 
that some highly purified cottonseed oils react so faintly with 
nitric acid that samples containing as much as 10 per cent, 
showed no reaction. 

The following is a summary of tests adapted to detection of 
the particular adulterations noted: 

Cottonseed Oil. Halphen's test; nitric acid color test; 



COTTONSEED OIL 171 

Bechi's test; iodin number; Livache's test; temperature re- 
actions; viscosity of soap solution. Brulle's test. 

Arachis Oil. Viscosity of soap solution; determination 
of arachidic acid ; iodin number. Brulle's test. 

Rape Oil. Iodin number; Palas' test; melting and solid- 
ifying points of acids ; acetic acid test ; refractive index. 

Sesame Oil. Furfural tests; pyrogallol test; iodin absorp- 
tion; temperature reactions ; saponification value. 

Some true olive oils give a reaction simulating sesame oil with 
the furfural test, but this confusion may be avoided by using 
the mixed fatty acids; the olive oil acids do not give the reaction. 

Lard Oil. Melting-point of fatty acids; odor of lard on 
warming. 

Seed Oils collectively. Separation of cholesterol analogs. 

Castor Oil. Solubility in acetic acid in the cold; solubil- 
ity in absolute alcohol; specific gravity. 

CuRCAS Oil. Iodin value; saponification value. Treated 
with nitric acid and copper, an intense reddish-brown is pro- 
duced in presence of as little as 10 per cent, of curcas oil. 

Hydrocarbon Oils. Determination of unsaponifiable mat- 
ter. 

Green olive oil has been imitated by coloring other oils with 
copper acetate. All green oils should be tested for copper by 
boiling with hydrochloric acid and testing the acid solution, 
as described on p. 58. 

COTTONSEED OIL 

Cottonseed oil is obtained from seeds of several species of 
Gossypium. The crude product is dark red. It is refined by 
treatment with alkali. The refined oil is pale yellow, of pleas- 
ant flavor, and neutral, but becomes rancid gradually, when free 
acid is also formed and a so-called ''stearin" deposited. The 
better grades of oil are sold after being freed from stearin by 
chilling or long standing. The refined oil is used for cooking 



172 FOOD ANALYSIS 

purposes and as a salad oil, as an adulterant for olive oil, butter, 
lard, and lard oil, and in the manufacture of butter substitutes. 
It is so cheap that it is but little liable to adulteration, except 
possibly with mineral oils. 

Cottonseed oil contains stearin, palmitin, olein, and linolin. 
A small proportion of a hydroxy-ester is said to be present. 

Cottonseed Stearin. — This is a commercial name of the solid 
fat deposited on standing or by cooling the oil and pressing. 
The product differs according to the completeness with which 
the oil has been separated. The proportion of true stearin 
appears to be very low. A sample examined by Hehner & 
Mitchell yielded only 3 per cent, of stearic acid. As ordinarily 
obtained the fat is light yellow and of the consistency of butter. 
It is largely used in the preparation of substitutes for butter 
and lard. 

The following arc some of the constants of this fat: 

Specific gravity, ^^ = 0.923 -^„ -^ 0.864 to 0.869 ^^o. 

Solidifying-point, 26° to 40°; titer test, 16°. 

Saponification value, .194-195. 
lodin value, 89-104. 

Mixed Fatty Acids. 

Solidifying-point 35°. 

Melting-point, 27° to 30°. 

lodin number, 94. 

Cottonseed stearin responds to the color tests for cottonseed 
oil. 

Another variety of so-called cottonseed stearin is the solid 
portion of the fatty acids separated from the oil in the pro- 
cess of purification by alkali. It consists chiefly of stearic 
acid and is employed in soap-making. 

MAIZE OIL CORN OIL 

Maize oil is obtained by expression from the seeds of the 
Zea Mays L., either directly or after they have been used for 



MAIZE OIL CORN OIL 1 73 

the preparation of alcohol. The latter product contains much 
free acid. The most recent and extended investigation of this 
oil is that made by Vulte & Gibson.^^ Data furnished by them, 
together with some from other sources, have been incorporated 
in the tables on pages 164 and 165. The follov^ing additional 
figures are from their paper. 

Acid value, 2.25. 

Free acid (percentage), 1.12. 

Insoluble acid, 92.2. 

Elaidin test, Orange-yellow deposit. 

Bechi's test, Dark brown. 

Many esters are present, as* the following acids have been 
obtained from the saponified material: Formic, acetic, stearic, 
palmitic, arachidic, hypogeic, oleic, linolic, ricinolic (probably), 
and, according to some investigators, caproic, caprylic, and 
capric. The results of different investigators do not agree in 
some points. Hehner & Mitchell were unable to find stearin 
in a sample examined by them. J. C. Smith found volatile 
acids equivalent to a Reichert number between 2 and 3. Hop- 
kins found no volatile acids in the sample examined by him. 

The oil is practically without drying power at the ordinary 
temperature. According to Smith, no decided siccative prop- 
erties are communicated to it by simply "boiling" or by the 
addition of litharge. On passing a current of air through it 
for an hour at a temperature of 150°, it becomes slightly darker 
and rather more viscous, but not to the same extent as cotton- 
seed oil. If to the oil so treated a small quantity of manganese 
borate be added, slight siccative properties are acquired, and 
a thin film on lead dries in from 10 to 20 hours, but not com- 
pletely. Hopkins found that on heating the untreated oil in 
the water-oven, a small amount of oxygen was absorbed, the 
increase in weight amounting to about i per cent, at the end of 
24 hours. 

The unsaponifiable matter was higli in the samples exam- 



174 FOOD ANALYSIS 

incd by Vullc & Oibsoii, the thok'sUTol analog (probably si- 
tosterol) being 1.4 per cent, and lecithin about 1.1 per cent. 

Gill &: Tufts propose to detect maize oil in cottonseed oil by 
applying the method described on page 161. From known 
mixtures of the two oils, they obtain the following weights of 
material the melting-point of which in each case coincided 
with that of sitosterol: 

Pure cottonseed, 50 grams yielded 0.095 

Cottonseed 45, maize 5, " " 0.120 

40, 10, O.IO 

A characteristic reaction of the oil is to dissolve it in carbon 
disulfid, add a drop of sulfuric acid and allow the mixture to 
stand for 24 hours, when it will become violet. 

ARACHIS OIL 

Arachis oil — also called peanut, ground-nut, and earth-nut 
oil — is obtained from the seed of the Arachis hypogcPM L. The 
cold expressed oil from the first runnings is nearly colorless, 
and that of the second expression usually of a pale greenish- 
yellow. It has an agreeable odor and flavor, but may be ob- 
tained nearly odorless and tasteless. It contains olein, pal- 
mitin, stearin, arachin, lignocerin, and probably hypogein. 
It is used as a salad oil. So-called ''peanut butter" consists 
simply of the ground roasted nuts. The principal use of the oil 
is as an adulterant for olive oil. The specific gravity and chemi- 
cal constants of the two oils are so nearly alike that the detec- 
tion of the admixture by these data is hardly possible. The 
determination of the iodin value is occasionally of use, but the 
only reliable method is that of Renard, depending upon the 
estimation of the amount of arachidic acid, or, more properly 
speaking, of the arachidic and lignoceric acids, since later in- 
vestigation has shown that the body separated and weighed 
as arachidic acid consists of both, lignoceric acid being in larger 
proportion. The method is laborious, and requires considerable 



ARACHIS OIL 175 

care in its performance; many shorter methods have been pro- 
posed, none of which are as satisfactory as the original method, 
which in its most improved form is described by Archbutt, as 
follows : 

10 grams of the oil are saponified in a deep porcelain basin, 
using 8 c.c. of aqueous sodium hydroxid solution (50 grams in 
100 c.c.) and 70 c.c. of alcohol. The basin is covered, the mass 
gently evaporated to about 20 c.c, rinsed with hot water into 
a separating funnel, mixed with slight excess of hydrochloric 
acid, and shaken with ether to dissolve fatty acids. Two 
extractions are sufficient. After washing the ether with 
water, it is distilled in a 250 c.c. flask, the fatty acids dried by 
heating the flask on a steam-bath and sucking out the vapor, 
and then dissolved in the hot flask in 50 c.c. of 90 per cent, 
alcohol. The solution must not be allowed to cool below about 
38°, lest crystals of lignoceric or arachidic acid should separate. 
5 c.c. of a 20 per cent, aqueous solution of lead acetate are added 
and the mixture cooled to about 15°, shaken, allowed to stand 
for half an hour, washed only once with ether, the mass rinsed 
back into the flask with a spray of ether, and digested with 
ether for a short time; then again filtered and again rinsed back. 
After doing this about four times, the lead oleate will be dis- 
solved. 

The filter is opened in a large plain funnel placed in the neck 
of a separating funnel, and the soaps at once rinsed into the 
separator with a jet of ether. The material that adheres to 
the paper and flask is decomposed and transferred by rinsing 
with hot dilute hydrochloric acid, followed by ether. About 
20 c.c. of hydrochloric acid (i.io sp. gr.) are poured into the 
separator, shaken well to decompose the lead soaps, the aqueous 
liquid drawn off, the ether repeatedly washed with small quan- 
tities of cold water until the lead chlorid is removed, distilled 
in a 250 c.c. flask, and the residual fatty acids thoroughly dried 
by heating on a steam-bath. 50 c.c. of ethyl alcohol of exactly 



176 FOOD ANALYSIS 

90 per cent, strength (sp. gr. 0.834) are poured into the flask, 
which is then closed with a cork carrying a thermometer, heated 
cautiously until the fatty acids have completely dissolved, and 
cooled to 15°, when lignoceric and arachidic acids, if present, 
will crystallize out, either at 'once or shortly. 

To estimate the amount, the flask should be kept for one 
hour, with occasional agitation, in a water-bath at either 15° 
or 20°, or at some intermediate fixed temperature which is 
nearest to that of the laboratory, the crystals collected on a 
small filter, using only the filtrate to rinse the flask, and washed 
with three portions of 10 c.c. each of 90 per cent, alcohol, at 
the same fixed temperature. A paper filter may be used, but 
a Gooch filter, used with gentle suction, is better, as the mother 
liquid is more perfectly removed and the washing more thorough. 
The filtrate and washings with 90 per cent, alcohol are poured 
into a measuring cylinder, and the acids thoroughly washed 
with 70 per cent, alcohol, in which arachidic and lignoceric 
acids are quite insoluble, until some of the washings give no 
precipitate when diluted with water. These washings are 
thrown aw^ay. It is not absolutely necessary, but it is advisable 
to redissolve the fatty acids thus obtained in 50 c.c. of 90 per 
cent, alcohol, and recrystallize them, filtering and washing as 
before, adding the filtrate and washings with 90 per cent, alcohol 
to the first quantity in the measuring cylinder. Pure arachidic 
and lignoceric acids are thus obtained, and are dissolved off" the 
filter with boiling ether, distilled down, and weighed in a tared 
flask after drying at 100° for an hour. To the weight obtained 
is to be added the amount dissolved by the 90 per cent, alcohol, 
which is calculated from the following table, based on deter- 
minations made by Tortelli & Ruggeri, and confirmed by Arch- 
butt. It will be noticed that the amount dissolved varies ac- 
cording to the weight of mixed acids obtained : 



0.033 
0.048 ^ 


0.039 
0.056 


0.046 
0.064 


0-055 
0.061 


0.064 
0.070 


0.074 
0.080 


0.064 
0.067 


0.074 
0.077 


0.085 
0.088 


0.069 
0.070 


0.079 
0.080 


0.090 
0.091 


0.071 


0.081 


0.091 



SESAME OIL 177 

Weight of Aeachidic and Correction per 100 c.c of 90 Per Cent. 

LiGNOCERic Acids Alcohol Used for Crystallization 

(Gram). and Washing (Gram). 

(15° C.) (i7-5°C.) (20° C.) 

O.I or less, 0.033 

0.2 

0-3 
0.4 

0.5 
0.6 
07 
0.8 
0.9 and upward, 0.071 

The proportion of arachidic and lignoceric acids which has 
been obtained by different observers from arachis oil is very 
fairly constant, averaging about 5 per cent., so that the amount 
of these acids found in any given mixture of oils, multiplied 
by 20, will give a close approximation to the amount of arachis 
oil present. 

SESAME OIL 

Sesame oil (also called Gingli and Teel oil) is obtained from 
the seeds of the Sesamum orientale L. and S. indicum L. The 
cold expressed oil is yellow and of pleasant taste. It consists 
of stearin, palmitin, olein, and linolin, with other bodies not 
clearly understood. 

Sesame oil has been used as a compulsory addition to butter- 
substitutes, in order to facilitate the detection of these. It is 
readily recognized by the furfural and pyrogallol tests. 

Adulteration. — Sesame oil is liable to adulteration, more 
especially with cottonseed, arachis, poppyseed, and rape oils. 
These may be detected as follows: 

Cottonseed oil. Halphen's, nitric acid, and Bechi's tests; 
Livache's test; melting-point of the fatty acids. 

Rape oil. Saponification value; specific gravity; solidifying 
and melting points of the fatty acids. 

Poppyseed oil. lodin value; temperature reactions. 

Arachis oil. Specific gravity; determination of arachidic 
acid. 



lyS FOOD ANALYSIS 

RAPE OIL 

Rape oil is obtained from several varieties of the Brassica 
campestris L. The oils derived from all of these are, as a rule, 
described indiscriminately rape oil or colza oil; but on the 
continent of Europe "colza oil" is sometimes taken to mean 
only that from a particular variety {napus). The physical and 
chemical characters of all the varieties appear to be practically 
identical. 

Rape oil is pale yellov^, has a peculiar smell, and rather an 
unpleasant taste. It consists chiefly of stearin, olein, and 
erucin. It also contains a small proportion of arachidin. 
About 0.4 per cent, of arachidic acid is said to have been sepa- 
rated from it. It is very liable to adulteration, but is of interest 
here only as an adulterant of olive oil. The physical and 
chemical characters are given in the tables on pages 164 and 165. 

Palas^ test. — A dilute solution of fuchsin (about i per cent.) 
and a strong solution of sodium acid sulfite (about 30 per cent.) 
are prepared separately. 20 c.c. of each of these are mixed, 
200 c.c. of water added and 5 c.c. of strong sulfuric acid. When 
the solution is decolorized, 10 c.c. of the sample should be 
shaken v^ith it. A partial restoration of color will occur if 
rape oil be present. It will be well to shake in a vessel full of 
the mixture, as contact of air may produce color. It must also 
be borne in mind that several aldehydes, especially formalde- 
hyde, will produce color with this test. 

COCONUT OIL 

Coconut oil is obtained from kernels of the coconut (species 
of Cocos), being usually expressed with aid of heat. It is nearly 
white and about the consistency of butter; has the taste and odor 
of the coconut. It contains palmitin and stearin, much myristin 
and laurin, with some caprin, caproin, and caprylin. It gives, 
therefore, a notable amount of volatile acids and soluble acids. 



CACAO-BUTTER 1 79 

By treatment with alcohol and animal charcoal, a white neutral 
product of agreeable flavor and good keeping qualities is ob- 
tained which is sold for food purposes under fanciful names, 
such as "vegetable butter," "vegetaline," "laureol," "nuco- 
line." By submitting the oil to pressure products termed 
"coconut olein" and "coconut stearin" are obtained. From 
samples of these, Allen has obtained the following data : 

Sp. Gr. (water at 15.5° = i) Solidifying- Melting- Reichert 

AT 15.5°; AT 98-99°. POINT. POINT. NuMBER. 

Olein, 0.926 0.871 4 rising to 8 5.6 

Stearin, solid 0.869 21.5 rising to 26 28.5 3.1 

For its recognition, the Reichert-Meissl number is most 
satisfactory. (See the constants on page 165.) 

CACAO-BUTTER 

Cacao-butter is the fat expressed from cacao beans. It is 
yellowish- white, becoming paler on keeping, possesses the 
pleasant odor and flavor of chocolate, is solid at ordinary tem- 
peratures, but easily melts in the mouth. It consists chiefly of 
stearin, palmitin, and laurin, with small proportions of arach- 
idin, linolin, formin, acetin, and butyrin. It is insoluble in 90 
per cent, alcohol, but dissolves in 5 parts of boiling absolute 
alcohol. 

Adulteration. — The common adulterants of cacao-butter 
are tallow, stearic acid, lard, parafhn wax, beeswax, coconut 
and arachis oils. The constants will usually suffice for their 
detection. 

Stearic acid is indicated by the high acid value ; 

Paraffin or beeswax, by the low saponification^ value and 
high proportion of unsaponifiable matter; 

Vegetable oils, by the increased iodin value and lower melt- 
ing-point of the fatty acids; 

Coconut oil by the low iodin value, high saponification value, 
and moderately high Reichert number. 

The following special tests are also useful: 



l8o FOOD ANALYSIS 

Bjorklaiid's test. — 3 grams of the fat arc mixed in a test- 
tube with 6 grams of ether, the test-tube closed with a cork, 
and solution efifected, if possible by shaking. When wax 
is present, a cloudy liquid results which is not changed on 
warming. If the solution is clear, the tube is placed in melting 
ice and the time observ^ed after which the solution begins to 
become milky or to deposit white flakes; then the temperature 
is noted at which the mixture becomes clear on removing from 
the ice-water. Pure cacao-butter solution becomes cloudy in 
10 or 15 minutes, and becomes clear again at 19° to 20°. With 
cacao-butter containing 5 per cent, of tallow, these figures 
are 8 minutes and 22° respectively; 10 per cent, of tallow, 7 
minutes and 25°. 

Filsinger suggests a modified ether test: 2 grams of the fat 
are melted in a graduated tube with 6 c.c. of a mixture of 4 
volumes of ether (sp. gr. 0.725) and 2 volumes of alcohol (sp. 
gr. 0.810), shaken, and set aside. The pure fat gives a solution 
that remains clear, even on cooling to 0°. 

Hager recommends the following test: About i gram of 
the fat is warmed with 2 to 8 grams of anilin until dissolved; 
the mixture is allowed to stand one hour at 15° or one and a 
half hours at 17° to 20°. Pure cacao-butter floats as a liquid 
layer on the anilin. If the sample contain tallow, stearic acid, 
or a little parafhn, particles, which remain hanging on the upper 
wall on gentle agitation, are formed in the oily layer. If wax 
or much paraffm be present, the layer solidifies. If much 
stearic acid be present, layers wuU not form, but the whole will 
solidify to a crystalline mass. The oily layer from pure cacao- 
butter hardens only after many hours. A parallel test should 
be made with a sample of known purity. 

LARD 

Strictly speaking, lard is the fat obtained from the mem- 
branes about the kidneys and intestines of the common hog. 



LARD l8l 

Commercial lard consists of the mixed fat from various parts 
of the animal. 
U.S. Standard. 

Lard is the rendered fresh fat from slaughtered, healthy 
hogs, free from rancidity, and containing not more than i 
per cent, of substances not fat (other than fatty acids), 
necessarily incorporated in the process of rendering. 

Leaf lard is the lard rendered at moderately high tempera- 
tures from the internal fat of the abdomen of the hog, excluding 
that adherent to the intestines, and has a-n iodin number not 
greater than 60. 

Neutral lard is lard rendered at low temperature. 

The following grades have also been given, but are not 
included in the official definitions. The requirement of not 
over 60 for iodin number of standard lard seems somewhat 
severe. 

Choice Kettle-rendered Lard. — Choice Lard. — Portions of the 
leaf, together with the fat cut from the backs, are rendered in 
steam- jacketed open kettles. The hide is removed from the 
back-fat before rendering. 

Prime Steam Lard. — The whole head of the hog, after the 
removal of the jowl, is used for rendering. The fat from the 
small intestines and fat attached to the heart are also used. 
The back-fat and trimmings and the leaf may also be used. 
Prime steam lard, therefore, may represent the fat of the whole 
animal, or only portions. 

A lower grade is made from intestines. The definition of 
the term as used by hog-packers is: everything inside of a 
hog except the lungs and the heart, or, in other words, the ab- 
dominal viscera. 

Lard consists of stearin, palmitin, and olein, with a small 
amount of linolin. Hehner & Mitchell obtained stearic acid 
in proportions varying from 6 to 16 per cent. The unsaponifi- 
able matter is small; Allen & Thomson found 0.23 per cent. 



1 82 FOOD ANALYSIS 

American and European lards differ appreciably in some 
analytic characters, as exhibited in the following table: 

Sp. Gr. -• loDiN Number. 
IS 

American Lards: 

From head 0.8632 65.9 

" back, 0.8616 63.8 

" leaf, 0.8626 61.4 

European Lards: 

From back, 0.8607 ^o-S 

" kidney, 0.8590 52.6 

" leaf, 0.8588 53.1 

More marked differences in the iodin value of fat from dif- 
ferent parts of the animal have been noted by other observers. 

Fresh lard usually contains little free acid, generally from 
0.1 to 0.4 per cent., but the proportion may rise above i per 
cent. On exposure to the air the amount increases consider- 
ably. Spaeth has made a number of determinations of free 
acid of samples kept in loosely-corked flasks. The following is 
a summary of the results obtained : 

Fresh. i Year Old. 3 Years Old. 

Free acid calculated as oleic, . . 0.01310 0.45 0.5110 6.05 2.81014.2 
Iodin number, 63.2 1051.7 55.4 1036.7 41.11021.5 

Adulteration. — Lard is much adulterated, especially with 
cottonseed oil, cottonseed-stearin, beef-stearin, and excess of 
water. Articles containing no lard have often been sold under 
the name "refined lard." More recently such preparations 
have been designated "lard compound" or "compound lard." 
Maize, sesame, and arachis oils may be present in these articles. 
Much attention has been given to the examination of com- 
mercial lards, and the follow^ing is a summary of the more 
trustworthy of the methods. A comparison of constants will 
be found on pages 164 and 165. 

Specific Gravity. — The specific gravity of lard is usually be- 
tween 0.860 and 0.861. The usual adulterants, except beef- 



LARD 183 

stearin, tend to raise the specific gravity, but they may be 
corrected by addition of vegetable oils. Wainwright ob- 
tained valuable data by compressing the sample in muslin or 
linen at ordinary temperatures and examining the more fluid 
portion. 

Melting-point. — This datum is usually of little value. Goske 
obtained some useful results by applying the titer-test (p. 11). 
Pure lards gave figures ranging from 23° to 30°; lard adul- 
terated with tallow and lard oil, from 29.7° to 36°. The solidi- 
fying-point of the fatty acids may be of value in detecting maize 
oil. 

lodin Number. — This differs considerably according to the 
part of the animal from which the sample is derived. The 
following table has been compiled from the results of many 
observers : 

American Lards. 
Head, 63 . to 85 ; average, 75 



Foot, 63 

Ham, 66 

Back, 61 

Leaf, 52 

Intestines, 60 



to 77; average, 70 

to 69; average, 67 

5 to 66.7; average, 64 

5 to 66.7; average, 59 



English lards may give figures 6 or 8 units lower. 

American steam-lard derived from different parts of the 
animal has an iodin value of about 59 to 66, but the effect of 
age on this must not be forgotten (see page 182). As a rule, 
the iodin value of mixtures of lard, beef-stearin, and lard oil 
is well within these limits, so that normal iodin value is not 
proof of purity. The addition of vegetable oils raises the figure 
notably, but, according to Lewkowitsch,^^ the iodin value of the 
liquid fatty acids is the best method of detecting admixture 
of vegetable fats. With American lard, the figure is between 
97 and 106; and with European lards, between 90 and 96. 
Should a sample give a value within the above limits, it must 



184 FOOD ANALYSIS 

be further examined for beef-stearin and coconut oil, since 
these may be added with a vegetable oil to bring the figure 
within the limits of normal lard. 

Thermal Test. — The rise of temperature with sulfuric acid, 
and more especially the heat of bromination, is of service in 
the detection of cottonseed products. The results with Mau- 
mene's test, as reported, differ greatly. It is advisable to per- 
form tests with samples of pure lard and cottonseed oil side 
by side with the suspected sample. The initial temperature 
may be about 35° or 40°. Care should be taken that the sample 
contains no water. 

Rejractometric Examination. — The examination of lard by 
the refractometcr or the butyrorefractometer is of value. Vege- 
table oils are readily detected, but the indications in the case 
of beef tallow and stearin are not so satisfactory. According 
to Jean, better results are obtained by operating on the liquid 
fatty acids. The following table is compiled from the results 
of Jean, Dupont, and other observ^ers. The figures were obtained 
by means of a refractometer different from those figured on 
page 154, but the table has value for the comparative results. 
The liquid fatty acids may be prepared as described on page 
141. Jean, whose figures are given in the table, prepared them 
by Sear's process: 50 grams of the lard are saponified, the 
fatty acids separated by addition of acid, washed with hot 
water, and mixed in a flask together with 250 c.c. of carbon 
disulfid and 8 to 10 grams of zinc oxid. The zinc salts of the 
liquid fatty acids dissolve in the carbon disulfid, and can thus 
be separated from the solid fatty acids. The carbon disulfid 
is evaporated, the fatty acids liberated with hydrochloric 
acid, well washed with hot water, and dried at a temperature 
of 120°. 



LARD 



185 



Degrees in Oleorefeactometer. 
Fat. 



Liquid Fatty 
Acids. 



American lard, mixed, 

" . " leaf, 

" " foot, back, head, etc., . 
European " 

" " stearin, 



Beef tallow,. 
" stearin. 
Veal " 
Coconut oil,. 



-7 

— 4 to — 1 1 

— 12 to — 13 

— ID to — II 

— 16 to — 17 

-34 
-19 

-54 



Cottonseed oil, '. + 12 to +23 

usually +20 

" stearin, +25 

Arachis oil, + 3 -5 to + 7 

Sesame " + 13 to + 18 



European lard with 20 per cent, cottonseed oil, . 



cent 



10 
30 
50 
20 
20 
50 



stearin, 



sesame oil,, 
arachis " . 
beef tallow, . 



-6 
-7. 
-3 

+ I 



-14 



40; beef fat, 40; cottonseed oil, 20 per 



European lard 60; mutton tallow, 25; arachis oil, 15 
per cent., 

European steam lard, 60; beef tallow, 15; arachis oil, 
25 per cent., 



13 



-30 



-40 



+ 10 
+ 20 

-15 
-18 



— 20 
-23 
-33 

-24 

— 22 



Special Tests. 

Seed Oils (cottonseed, sesame, arachis, and maize); iodin 
number of the Hquid fatty acids. Separation of cholesterol 
analogs. The oils are further specifically identified as follows: 

Cottonseed Oil. — Lard from animals fed liberally on cotton- 
seed products may give faint reactions for cottonseed oil by the 
qualitative tests. Halphen's test is the most satisfactory. The 
nitric acid and Bechi's tests may also be applied. Pure lard 
17 



l86 FOOD ANALYSIS 

that has Ijccn exposed to the air may respond to Bechi's test, 
so that the sample should be carefully taken from the interior 
of the mass. On the other hand, cottonseed oil that has been 
heated for a short time to 240° no longer responds to this test, 
and reacts to Halphen's test with diminished intensity. 

Jones suggested sulfur chlorid as a test for cottonseed oil, 
which forms with it a hard mass partly insoluble in carbon 
disulfid. Lewkowitsch has found the method useful, and ap- 
plies it as follows: 5 grams of the fat are dissolved in 2 c.c. 
of carbon disulfid, 2 c.c. of sulfur chlorid are added, and the 
mixture heated on the water-bath. The following results were 
obtained with mixtures of lard and cottonseed oil: 



Cottonseed Oil Per- 
centage. 

None, No reaction. 

ID Thickens after 35 minutes. 

20 " "30 

30 " " 26 

40 " " 18 

50 Solid after 10 minutes. 

60 " " 8 

70 " " 7 

80 " " 6 

90 " " 4 

100 " " 3 



It is recommended to test the sample side by side with pure 
lard, or with mixtures of known composition. 

Cottonseed Stearin. — For the detection of this the above tests 
for cottonseed oil should be applied, also specific gravity de- 
termination. 

Arachis Oil. — Renard's method should be applied (page 175). 

Sesame Oil. — Furfural and pyrogallol tests should be applied 
fpage 165). 

Maize Oil. — In the absence of other seed oils, the melting- 
point of the mixed fatty acids is of use. 



Solubility of 


Product 


IN Carbon Disulfid. 


Completely soluble. 


(( 


(( 


52.0 per cent. 


soluble. 


39-6 " 


ii 


34-8 " 


<< 


37.4 per cent. 


soluble. 


30.6 - 


a 


32.6 " 


<( 


30.0 " 


a 


24.0 " 


it 



LARD 187 

Coconut Oil. — The iodin number, saponification value, and 
Reichert number are useful data. 

Tallow. — Beef-stearin. — Belfield proposed to use the follow- 
ing: The sample is dissolved in warm ether and the solution 
is cooled slowly and the crystals deposited are examined under 
the microscope. Crystallization should take place as slowly 
as possible. A good method is to place a cotton plug in the 
mouth of the tube, and allow the ether to evaporate slowly. 
The crystals from pure lard are usually in the form of plates 
with oblique terminals. 

Cochran finds the following method satisfactory: 

2 c.c. of the melted fat are mixed with 22 c.c. of fusel oil 
and the mixture warmed to about blood heat, and when com- 
plete solution is effected it is allowed to cool slowly to 16° or 
17° and maintained at this temperature for several hours, dur- 
ing which a crystalline deposit forms. This is transferred to 
a filter, the fusel oil drained off as far as possible, and a part 
or whole of the residue dissolved in ether in a test-tube, the 
mouth of the tube being plugged with cotton. The crystals 
which form on standing may be mounted in cottonseed oil 
and examined under a microscope. 

The proportion of beef-stearin present may be approxi- 
mately estimated by Stock's modification of Belfield's test. 
It consists in comparing the crystals obtained from an ethereal 
solution with those from two standard sets of mixtures, the first 
consisting of pure lard melting at 34° to 35°, with 5, 10, 15, 
and 20 per cent, of beef-stearin melting at 56°; the second of 
pure lard, of melting-point of 39° to 40°, with 5, 10, 15, and 20 
per cent, of beef-stearin melting at 50°. The process is as fol- 
lows: The melting-point of the sample is determined by the 
capillary tube method. Suppose the melting-point be found 
at 34°, 3 c.c. of the melted fat are run into a graduated cylinder 
of about 25 c.c. capacity; 21 c.c. of ether are added, and the 
fat dissolved at 20° to 25°; 3 c.c. of each of the first set of mix- 



1 88 FOOD ANALYSIS 

tures are treated in exactly the same way. The hve cylinders 
are cooled down to 13°, and allowed to remain at that tem- 
perature for 24 hours. An approximate estimate as to the 
amount of the adulterant is arrived at by reading off the ap- 
parent volume of the deposited crystals. The ether is then 
poured off as far as possible, and 10 c.c. of fresh ether at 13° 
are added in each case. The cylinders are again shaken, cooled 
as before, and the proportion of cr}'stals read off as before. 
Finally, the contents are emptied into weighed shallow beakers, 
the ether drained off carefully, the mass allowed to dry for 15 
minutes at 100°, and weighed. The weight obtained for the 
sample under examination is compared with the weight of the 
crystals obtained from the standard nearest to it. The second 
set of mixtures is used for samples of higher melting-point. 
The actual presence of beef-fat must be proved by microscopic 
examination, when the characteristic tufts are seen. No 
sample of pure lard melting below' 39° yielded more than o.oi i 
gram of cr}^stals under the above conditions. A sample of the 
melting-point 45.8° gave, however, 0.146 gram of crs'stals. 

Beef-fat crystallizing from ether forms spherical masses, 
which when pressed under a cover- glass become fan- shaped 
tufts. Under high magnification the individual crystals still 
appear in needle-like form quite distinct from the plates pro- 
duced by lard. In samples of lard containing beef-fat the 
crystals obtained are not a mixture of those t}'pical of the two 
substances, but usually uniform and resemble those of lard 
somewhat modified. In some cases the manner of aggregation 
is similar to that of beef-fat cr}'stals, but the individual cr}'s- 
tals, instead of being needle-shaped, have more the appearance 
of those from lard. It will often be necessary to recrystallize 
repeatedly under varying conditions, to get characteristic crys- 
tals. 



BUTTER-FAT 1 89 

BUTTER-FAT 

The fat of cow's milk is the only one of importance, and 
this is only known commercially in the form of butter, a mix- 
ture of the fat with varying proportions of water, salt, curd, 
coloring-matter, sometimes boric acid, and other fats. For 
methods of analysis and distinction of butter-fat from other 
fats, see under "Milk Products." 



MILK AND MILK PRODUCTS 

Milk, the nutritive secretion of nursing mammals, consists 
of water, fat, proteids, sugar, and mineral matters. Cow's 
milk is meant in all cases, unless otherwise stated. 

Fat. — This occurs in globules varying from 0.0015 mm. to 
0.005 "^^"^"^- i^ diameter, in a condition which prevents spon- 
taneous coalescence. It is peculiar among animal fats in con- 
taining a notable proportion of acid radicles with a small num- 
ber of carbon atoms. 

Proteids.— The nature of the proteids of milk has been 
much discussed, but it is now generally conceded that there are 
at least three forms, casein, albumin, and globulin, the casein 
being present in by far the greatest amount, and the globulin as 
traces only. 

Casein. — Casein is, probably in part, in combination with 
phosphates. It is precipitated by many substances among 
which are acids, rennet, and magnesium sulfate, but not by 
heat. Acids precipitate it by breaking up the combination 
with phosphates. The action of rennet is complex and probably 
partly hydrolytic, splitting the casein into several proteids, some 
of which are precipitated in the curd. Films of proteid matter 
occur abundantly in milk, for which reason it is distinctly 
opaque, even when nearly all the fat has been removed by 
centrifugal action. 

The albumin of milk appears to be a distinct form, and is 
called lactalbumin. It is not precipitated by dilute acids, but 
is coagulated by heating to 70° — 75°. The proportion in cow's 
milk is usually from 0.35 to 0.50 per cent., but colostrum may 
contain much larger proportions. 

Globulin is present only in minute amounts in normal milk, 

190 



MILK AND MILK PRODUCTS IQI 

but colostrum may contain as much as 8 per cent. It is co- 
agulated on heating. 

Lactose. — This is a sugar peculiar to milk. 

Citric acid is a normal constituent of the milk of various 
animals. In human milk, the quantity is about 0.5 gram to 
the liter; in cow's milk, from i to 1.5 grams. It is not de- 
pendent on the citric acid present in the food. 

Wender states that the following enzyms exist in normal milk : 

Milk trypsin or galactase. This is a proteolytic enzym. It 
dissolves casein and is rendered inactive by exposure to a tem- 
perature of 76°. 

Milk-catalase. This can decompose hydrogen dioxid and 
similar compounds. It is rendered inactive by exposure to a 
temperature of 80°. 

Milk- per oxydase, an anerobic oxydase, that is, a body that 
has the power to decompose peroxids and carry the oxygen 
over to other substances. This is the substance which produces 
the reaction when milk, hydrogen dioxid and tincture of guaia- 
cum are mixed, by which a deep blue is obtained. This enzym 
is rendered inactive by exposure to a temperature of 83°. 

Minute amounts of nitrogenous bases occur in milk. 

Mineral Matter. — The ash of milk contains calcium, mag- 
nesium, iron, potassium, and sodium as chlorids, carbonates, 
sulfates, and phosphates. It does not exactly represent the 
salts present in milk. 

Richmond has determined the ratio of the ash to the solids 
not fat of 135 samples of milk. This was found to range from 
7.8 to 9.4 per cent., but more usually from 7.8 to 8.5 (average 
8.2) per cent. Many ashes were alkaline to turmeric, litmus, 
and phenolphthalein, the maximum alkalinity being 0.025 P^^ 
cent, calculated as sodium carbonate. 

The following table gives the approximate composition of 
some milks. Analyses of the milks of less important animals 
have been published, but the figures are of uncertain vahie, be- 



192 FOOD ANALYSIS 

cause it is not sure that the samples were of average character 
or the methods of analysis accurate: 

Huii.'VN. Cow. Mark. Goat. Ass. Gamoose. 

Fat, 3.5 4.0 I.I 4.3 1.6 5.6 

Sugar, 6.8 4.8 6.6 4.0 6.1 5.4 

Proteids, 1.5 3.5 1.9 4.6 2.2 3.8 

Ash, 0.2 0.7 0.3 0.6 0.5 i.o 

12.0 13.0 9.3 13.5 10.4 15.8 

Normal milk is an opaque white or yellowish-white fluid, 
with an odor recalling that of the animal, and a faint sweet 
taste. The opacity is due largely but not entirely to the fat 
globules. The reaction of freshly drawn milk to litmus is 
usually alkaline, but is sometimes amphoteric; that is, it turns 
the red paper blue and the blue paper red. The specific gravity 
varies between 1.027 and 1.035. ^^ usually undergoes a gradual 
augmentation (sometimes termed Recknagel's phenomenon) 
for a considerable time after the sample has been drawn. The 
increase may amount to two units (water being 1000). The 
specific gravity becomes stationary in about 5 hours if the milk 
be maintained as a temperature below 15°, but at a higher 
temperature it may require 24 hours to acquire constancy. The 
change is not entirely dependent on the escape of gases. 

Unless collected with special care and under conditions of 
extreme cleanliness, milk always contains many bacteria and 
animal matter of an offensive character, such as epithelium, 
blood and pus cells, particles of feces, and soil. 

At ordinary temperature milk soon undergoes decomposition, 
by which the milk sugar is converted principally into lactic acid, 
and the proteids partly decomposed and partly coagulated. 
The liquid becomes sour and the fat is inclosed in the coagu- 
lated casein. In the initial stages of decomposition the proteids 
frequently undergo transformations into substances which are 
the cause of the violent poisonous effects occasionally produced 
by ice-cream and other articles of food into the preparation of 
which milk enters. 



MILK AND MILK PRODUCTS 



193 



Boiling produces coagulation of the albumin, some caramel- 
ization of the sugar, and develops a greater facility of coales- 
cence on the part of the fat globules. Enzyms are rendered 
inert and most microbes are killed. 

When milk is allowed to stand, some of the fat rises gradually 
and forms a rich layer, constituting cream. The proportion 
of cream depends on several conditions. The amount formed 
in a given time cannot be taken as a measure of the richness of 
the milk. Water added to milk causes a more rapid separation 
of the cream. Centrifugal action separates nearly all of the 
fat. The following figures, given by D'Hout as averages, 
show this effect: 

Wh 

Specific gravity, 1032 

Total solids, 14 

Sugar, 4 

Casein, 3 

Ash, o 

Fat, 5 

Buttermilk is the residue after removal of the butter by churn- 
ing. Vieth gives the following analyses : 



Milk. 


Separated 


Milk. 


Cream. 


32 


1034 




1015 


.10 


9.6 




26.98 


.70 


5^05 




3^32 


•50 


3.62 




2.02 


•79 


0.78 




0.58 


•OS 


0.20 




21.95 



Total Solids. 


Fat. 


Solids not Fat. 


Ash. 


9^03 


0.63 


8.40 


0.70 


8.02 


0.65 


7-37 


1.29 


10.70 


0-54 


10.16 


0.82 



Whey or Milk- serum is the liquid freed from curd after 
precipitation by rennet or acids. In most cases it contains a 
notable amount of proteids, as shown in the following analyses 
by Cochran : 



Milk. 



Whey. 



otal solids. 


Solids not fat. 


Total solids. 


Proteids removed 


9.27 


9-13 


6.62 


2-51 


9.27 


9-13 


6.1 


3-'^^ 


14.05 


8.35 


6.62 


2-33 


7-71 


7.61 


5-98 


1.63 


8.91 


8.71 


6.50 


2.21 


18 









194 FOOD ANALYSIS 

The whey of any given milk has i)raclieally the same com- 
position, whether taken from the original milk, skimmed milk, 
or cream. 

Average Proportion oj Solids in Milk. — The most extensive 
data on this point are those obtained by \'ieth. The total 
number of samples was 120,540. The averages of the entire 
series are as follows : 

Fat, 4.1 per cent. 

Non-fatty solids, 8.8 

Total solids, 1 2 .9 " 

Richmond's results for several years have confirmed these 
figures. 

Seasonal Variations in the Composition oj Milk. — The poor- 
est quality usually occurs during the first half of the year, es- 
pecially in April. A low figure is also frequently noted about 
July. In autumn the quality rises, being highest in October 
and November. 

Deficient Solids. — The following are some instances of de- 
ficiency of solids in milk known to be genuine: 









Total 




Sp.Gr. 


Fat. 


S. X. F. 


Solids. 


.\XALVST. 


1029.6 


Z-Z^ 


7-95 


11-33 


Cochran. 


1030.0 


3(>2 


8.31 


"•93 


Cochran. 


1029.3 


3(>3 


8.02 


11.65 


Cochran. 


.... 


3-99 


8.36 


12-35 


Leffmann and Beam 




311 


8-33 


11.44 


Monthly averages N. 




305 


8.33 


11.38 - 


J. State Agricul- 




323 


8.44 


11.67) 


tural Exp. Station. 



The following analyses of milk from individual cows were 
made by Cochran. The samples were taken under precau- 
tions which insured their genuineness. The data are all direct 
determinations. The total solids were obtained by drying in 
the usual manner, and the fat by the L-B. method. Low milks 
have been often noted in the vicinity of Philadelphia. 



MILK AND MILK PRODUCTS 1 95 

Sp. Gr. Fat. S. N. F. Total Solids. 

1026.6 2.35 6.78 9.13 

1028.8 2.95 7.56 10.51 

1028.8 2.40 7.56 9.96 

1033.5 2.90 8.68 11.58 

The mixed milk from a herd of any considerable number Avill 
rarely, if ever, show a proportion of non-fatty solids less than 
8.5 per cent, nor less than 3.5 per cent, of fat. Cochran ex- 
amined the milk from each cow of a herd of 59, with the follow- 
ing results: 

Fat, 2.60 to 5.40. 

Total solids, 9.86 to 13.78. 

The average milk of the entire herd was : 

Fat, 3.76 per cent. 

Total solids, ^^-33 per cent. 

The average of nearly 100 determinations at the University 
of Wisconsin creamery during a protracted drought in 1895 
gave but a trifle over 8.5 per cent, solids not fat. The casein 
was low in this milk, while the sugar was about normal in 
amount. Similar conditions have been observed by Van Slyke 
at the New York station. 

Richmond states that when the non-fatty solids of genuine 
whole milk are low, the deficiency is principally in the milk 
sugar. 

Colostrum. — This is the secretion in the early stages of 
lactation, and differs from ordinary milk. It contains char- 
acteristic structures, known as colostrum corpuscles, and usually 
contains much less fat than fully developed milk, but a larger 
proportion of proteids. Colostrum coagulates on boiling. 
Lactose is in small amount. 
U. S. Standard. 

Milk (whole milk) is the lacteal secretion obtained by llie 
complete milking of one or more healthy cows, properly fed 
and kept, excluding that obtained within 15 days before and 



19^) FOOD ANALYSIS 

live days after calving, and contains not less than 12 per cent, 
of total solids, not less than 8.5 per cent, of solids not fat, and 
not less than 3.25 per cent, of milk fat. 

Blended milk is milk modified in its composition so as to 
have a definite and stated percentage of one or more of its 
constituents. 

Skim milk is milk from which a part or all of the cream has 
been removed and contains not less than 9.25 per cent, of milk 
solids. 
Analytic Processes. 

As already noted, the specific gravity of milk rises gradually 
for some time after it has been drawn, and the determination 
is to be made only after this action has ceased. This will re- 
quire about 5 hours after the milk is drawn, if it has been 
kept below 15°, but at a higher temperature it will be necessary 
to allow at least 12 hours. For all other determinations the 
milk must be analyzed as soon as possible. The following 
figures, published by Bevan, show that a considerable loss in 
total solids may occur in 24 hours: 

Total Solids. Loss. 

Evaporated immediately, 1 1 -73 

Evaporated after 24 hours, io-79 o-94 

Evaporated after 48 hours, io-3<^ i-35 

Evaporated after 120 hours, 9.42 2.31 

The decomposition is very irregular, and it is not possible 
to determine, by estimation of the lactic acid or other products, 
the original composition of the milk. The pipet used for taking 
a portion for analysis should have a wide opening, that no cream 
may be retained when the pipet is discharged. 

When rigid accuracy is not essential, it will suffice to measure 
the portions of milk taken for the determinations. Vieth uses 
a pipet graduated to deliver 5 grams, and finds that, working 
with whole and skimmed milk, under the ordinary variations 
of temperature, the error will not exceed o.i on the total solids 
and is less on the fat. 



MILK AND MILK PRODUCTS 1 97 

A good plan is to use a 5 c.c. pipet and to wash out that 
which adheres to the glass with a little water. The specific 
gravity of the milk being known, the amount taken can be 
calculated. The milk should be as near 15.5° as possible. 

Specific Gravity. — Air-bubbles are held rather tenaciously 
by milk, and care must be taken in mixing, preparatory to 
taking the specific gravity, to avoid as far as possible the 
inclosure of the air, and to allow sufficient time for the escape of 
any bubbles that may be present. The specific gravity of milk 
is understood to be taken at 15.5°; samples should be brought 
near to this. If at a few degrees above or below, it will suffice 
to make the determination at once and obtain the correct figure 
by reference to the annexed table. The specific gravity of 
normal milk varies between 1.028 and 1.035. The figure alone 
does not indicate the character of the sample, but taken in con- 
junction with the figure for fat or for total solids, it is of value 
as a check on the results furnished by other determinations. 

The simplest method of determining specific gravity is by 
the lactodensimeter, a delicate and accurately graduated hydro- 
meter. The instrument must be immersed carefully so as not 
to wet the stem above the point at which it will rest. The in- 
strument should be tested by immersion in distilled water at 
15.5° and milks of known specific gravity. 

The indications furnished by the lactodensimeter are suffi- 
ciently accurate for most purposes, but its employment neces- 
sitates a considerable amount of the sample. 

More accurate determination can be made by the methods 
detailed in the introductory part (page 3), the most suitable 
being the Sprengel tube. According to Richmond, the pyk- 
nometer is less suitable for rigidly accurate work, on account 
of the tendency of the cream to separate before the mass has 
acquired the standard temperature. 

Total Solids. — This determination may often be ma(k^ 
with sufficient accuracy for practical purposes by e\;ip()r;iliiig 



198 



FOOD ANALYSIS 



a measured volume {e. g., 3 or 5 c.c.) in a shallow nickel dish 
from 5 to 8 cm. in diameter. Nickel crucible-covers are suitable. 
The thin glass (Petri) dishes used for microbe culture are con- 
venient. When greater accuracy is required, and especially 
when the ash is to be determined, platinum dishes must be 
used. Satisfactory results may be secured by the following 
simple method: A flat platinum dish, t,.-^ cm. in diameter, 
with sides 0.5 cm. high, is provided with a thin flat watch-glass 
cover that tits rather closely. The total weight of the cover 



Find the lemperature of the milk in one of the horizontal lines and tlie specific 
gravity in the first vertical column. In the same line with this and the tempera- 
ture the corrected specific gravity is given. 



°F. 


50 .51* 


52 


53 


54 55 


56 


57 58 ' 59 


60 61 


62 


Sp. 1 

Gr. 1 
21 20.2 20.3 20.3 20.4 

1 1 


20.5 20.6 


1 
20.7 20.8 


20.9 20.9 


t 1 

21.0 21. 1 ' 21.2 

1 


22 


21.2 21.3 21.3 21.4 


21.5 21.6 


21.7 21.8 


21.9 21.9 


1 
22.0 j 22. 1 22.2 


23 


1 
22.2 22.3 22.3 22.4 22.5 22.6 22.7 22.8 


22.8 22.9 


23.0,23.1 


23.2 


24 


23.2 23.3 23.3 23.4 23.5 23.6 23.6 23.7 23.8 23.9 


24.0 ■ 24. 1 


24.2 


25 


24.1 24.2 


24-3 


24.4 


24.5 


24.6 


24.6 


24.7 24.8 


24.9 


25.0 


25- 1 


25.2 


26 


25.1 25.2 


25.2 


253 


254 


255 


25.6 


25.7 25.8 


25.9 


26.0 


26.1 


26.2 


27 


26.1 26.2 


26.2 


26.3 


26.4 


26.5 


26.6 


26.7 26.8 


26.9 


27.0 


27.1 


273 


2S 


1 
27.0 27.1 


27.2 


27.3 27.4 27.5 


27.6 


27.7 27.8 


27.9 


28.0 28.1 


28.3 


29 


28.0 28.1 28.2 


28.3 28.4 28.5 28.6 28.7 28.8 


28.9 


29.0 29.1 


29.3 


30 


29.0 29.1 29.1 


29.2 


29.3 29.4 29.6 29.7 29.8 29.9 


30.0 30.1 30.3 


31 


29.9 


30.0 30.1 


30.2 30.3 30.4 30.5 30.6 30. S 30.9 


31.0 31.2 31.3 


32 


309 


31.0 31. 1 


31.2 31.3 31.4 31.5 31.6 31.7 31.9 


32.0 32.2 32.3 

1 


33 


318 


31-9 320 


32.1 32.3 32.4 32.5 32.6 32.7 


32.9 


33-0 33-2 33-3 


34 32-r 329 33-0 


33-^ 33-2 


33-3 33-5 33-6 33-7 


33-9 


34.0 34.2 34.3 


35 33-^ 33-8 33-9 


340' 34-2 


34-3 


34-5 34-6 ,34.7 


34.9 


350 35-2 35-3 

1 1 


°C. 10 10.5 1 1. 1 

1 1 ^ 


II. 6 12.2 12.7 13.3 13.8 14.4 15.0 


15.5 16. 1 16.6 

1 i 



MILK AND MILK PRODUCTS 



199 



and dish is noted. 2 or 3 c.c. of the sample are run into the 
dish from the pipet, the watch-glass placed on, and the weight 
taken as rapidly as possible. The glass prevents appreciable 
loss from evaporation during an ordinary weighing. The cover 
is removed, the dish heated on the water-bath or in the water- 
oven, and weighed from, time to time (with cover on it) until the 
weight is sensibly constant. The percentage of residue can be 
easily calculated. About three hours may be required to secure 
constant weight. 



Find the temperature of the milk in one of the horizontal lines and the specific 
gravity in the first vertical column. In the same line with this and the tempera- 
ture the corrected specific gravity is given. 



'63 


64 


65 


66 


67 


68 


69 


70 


71 


72 


73 74 


75 


21.3 


21.4 


21-5 


21.6 


21.7 


21.8 


22.0 


22.1 


22.2 


22.3 


22.4 


22.5 


22.6 


22.3 


22.4 


22.5 


22.6 


22.7 


22.8 


23.0 


23.1 


23.2 


23-3 


23-4 


23-5 


23-7 


23-3 


23-4 


23-5 


23.6 


23-7 


23.8 


24.0 


24.1 


24.2 


24-3 


24.4 


24.6 


24.7 


24-3 


24.4 


24-5 


24.6 


24.7 


24.9 


25.0 


25- 1 


25.2 


25-3 


25-5 


25.6 


25-7 


25-3 


25-4 


25-5 


25.6 


25-7 


25-9 


26.0 


26.1 


26.2 


26.4 


26.5 


26.6 


26.8 


26.3 


26.5 


26.6 


26.7 


26.8 


27.0 


27.1 


27.2 


27-3 


27.4 


27-5 


27.7 


27.8 


27.4 


27-5 


27.6 


27.7 


27.8 


28.0 


28.1 


28.2 


28.3 


28.4 


28.6 


28.7 


28.9 


28.4 


28.5 


28.6 


28.7 


28.8 


29.0 


29.1 


29.2 


29.4 


29-5 


29.7 


29.8 


29.9 


29.4 


29-5 


29.6 


29.8 


29.9 


30.1 


30.2 


30-3 


30-4 


30-5 


30- 7 


30.9 


31.0 


30.4 


30-5 


30-7 


30.8 


30-9 


311 


31.2 


31-3 


31-5 31-6 


31-8 


31-9 


32.1 


314 


315 


31-7 


31-8 


32.0 


32.2 


32.2 


32.4 


32.5 32.6 


32.8 


33-0 


33-1 


32.5 


32.6 


32-7 


32.9 


330 


33-2 


33-3 


33-4 


33-6 


33-7 


33-9 


340 


34-2 


33-5 


33-6 


33-^ 


33-9 


34-0 


34-2 


34-3 


34-5 


34-6 


34-7 


34-9 


35-1 


35-2 


34-5 


34-6 


34-8 


34-9 


35-0 


35-2 


35-3 


35-5 


35-6 


35-8 


36.0 


36.1 


36.3 


35-5 


35-6 


35-8 


35-9 
18.8 


36.1 


36.2 


36.4 


36.5 


36.7 


36.8 


370 


37-2 


37-3 


17.2 


17.7 


18.3 


19.4 


20 


20.5 


21. 1 


21.6 


22.2 


22.7 


23-3 


23.S 



200 FOOD ANALYSIS 

The A. O. A. C. method is: Heat at ioo° to constant weight, 
about 3 grams in a tared platinum, aluminum or tin dish of 
5 cm. diameter, with or without the addition of 15 to 30 grams 
of sand. Cool and weigh. 

The use of aluminum or tin as substitutes for platinum is 
inadvisable, much better results will be obtained with nickel, 
porcelain or glass. 

Ash. — The residue from the determination of total solids is 
heated cautiously over the Bunsen burner, until a white ash 
is left. The result obtained in this manner is apt to be slightly 
low from loss of sodium chlorid. This may be avoided by 
heating the residue sufficiently to char it, extracting the sol- 
uble matter with a few cubic centimeters of water, and filtering 
(using paper extracted with hydrofluoric acid). The filter is 
added to the residue, the whole ashed, the filtrate then added, 
and the liquid evaporated carefully to dr\'ness. The ash of 
normal milk is about 0.7 per cent, and faintly alkaline. A 
marked degree of alkalinity and effervescence with hydro- 
chloric acid will suggest the addition of a carbonate. 

The method of the A. O. A. C. is as follows: In a weighed 
dish put 20 c.c. of milk from a weighing bottle; add 6 c.c. of 
nitric acid, evaporate to dryness, and burn at a low red heat 
till the ash is free from carbon. 

Fat. — Many methods for fat determination have been de- 
vised. The following will suffice for all practical work: 

Babcock Asbestos Method. — This is recommended by the A. O. 
A. C: Provide a hollow cylinder of perforated sheet metal 60 
mm. long and 20 mm. in diameter, closed 5 mm. from one end 
by a disk of the same material. The perforations should be 
about 0.7 mm. in diameter and 0.7 mm. apart. Fill the cylin- 
der loosely with from 1.5 to 2.5 grams of freshly ignited woolly 
asbestos free from fine or brittle material. Cool in a desiccator 
and weigh. Introduce a weighed quantity of milk (about 4 
grams) and dry at 100°. The cylinder is placed in the ex- 



MILK AND MILK PRODUCTS 20I 

traction tube and extracted with ether in the usual way. The 
ether is evaporated and the fat weighed. The extracted cyl- 
inder may be dried at ioo° and the fat checked by the loss in 
weight. A higher degree of accuracy is secured by performing 
the drying operation in hydrogen. 

Adams^ Method. — This consists essentially in spreading the 
milk over absorbent paper, drying, and extracting the fat in an 
extraction apparatus; the milk is distributed in an extremely 
thin layer, and by a selective action of the paper the larger 
portion of the fat is left on the surface. A paper, manufac- 
tured especially for this purpose by Schleicher & Schuell, is 
obtainable in strips of suitable size. Each of these yields to 
ether only from o.ooi to 0.002 gram of extract. 

Coils made of thick filter-paper, cut into strips 6 by 62 cm., 
are thoroughly extracted with ether and alcohol, or the weight 
of the extract corrected by a constant obtained for the paper. 
From a weighing bottle about 5 grams of the milk are trans- 
ferred to the coil by means of a pipet, care being taken to 
keep dry the end of the coil held in the fingers. The coil is 
placed, dry end down, on a piece of glass and dried for one hour, 
preferably in an atmosphere of hydrogen; it is then transferred 
to an extraction apparatus and extracted with absolute ether, 
petroleum spirit of boiling-point about 45° or, better, carbon 
tetrachlorid. The extracted fat is dried and weighed. 

The above procedure is very satisfactory, but the drying 
in hydrogen may usually be omitted. After the coil has re- 
ceived at least twenty washings, the flask is detached, the ether 
removed by distillation, and the fat dried by heating in an air- 
oven at about 105°, and occasionally blowing air through the 
flask. After cooling, the flask is wiped with a piece of silk, 
allowed to stand ten minutes, and weighed. 

Richmond states that to perform a rigidly accurate deter- 
mination attention to the following points is necessary: The 
ether must be anhydrous (drying over calcium chlorid and 



202 



FOOD ANALYSTS 



distilling is sufficicnlj. Schleicher &: SchuclTs fal-frec papers 
should be used, and one should be extracted without any milk 
on it, as a tare for the others. Four or live hours' extraction 
is necessary, and the coils should be well dried before extraction 
is begun. 

Thimble-shaped cases made of fat-free paper are now ob- 
tainable and arc convenient for holding the absorbent material 
on which the milk is spread. The fine texture prevents un- 
dissolved matter escaping. A case may 
be used repeatedly. Sour milk may be 
thinned with ammonium hydroxid before 
taking the portion for analysis. 

Werner-Schmid Method. — This is suita- 
ble for sour milk and for sweetened con- 
densed milk. I oc.c. of the milk are meas- 
ured into a long test- tube of 50 c.c. capac- 
ity, and 10 c.c. of strong hydrochloric acid 
added, or the milk may be weighed in a 
small beaker and washed into the tube 
with the acid. After mixing, the liquid 
is boiled i\ minutes, or the tube may be 
corked and heated in the water-bath from 
5 to 10 minutes, until the liquid turns 
dark brown. It must not be allowed to 
turn black. The tube and contents are 
cooled in water, 30 c.c. of well-washed ether added, shaken, 
and allowed to stand until the line of acid and ether is 
distinct. The cork is taken out, and a double-tube arrange- 
ment, like that of the ordinary wash-bottle, inserted. The 
stopper of this should be of cork and not of rubber, since 
it is difficult to slide the glass tube in rubber, and there is a pos- 
sibility, also, of the ether acting on the rubber and dissolving it. 
The lower end of the exit-tube is adjusted so as to rest im- 
mediately above the junction of the two liquids. The ethereal 




MILK AND MILK PRODUCTS 203 

solution of the fat is then blown out and received in a weighed 
flask. Two more portions of ether, 10 c.c. each, are shaken 
with the acid liquid, blown out, and added to the first. The 
ether is then distilled off and the fat dried and weighed as above. 

Centrifugal Methods. — Among the processes for the rapid 
determination of fat, those employing centrifugal action have 
been found most convenient. The following method, devised 
by Leffmann & Beam in 1889,^^ has proved satisfactory on 
the score of accuracy, simplicity, and ease of manipulation. 
This process, which antedates in its successful operation 
and public exhibition all the rapid centrifugal methods except 
the De Laval, is sometimes called the "Beimling" method, 
but Beimling was merely a patentee of a crude form of cen- 
trifugal machine, and had no part in devising the mixture for 
freeing the fat. The distinctive feature is the use of fusel oil, 
the effect of which is to produce a greater difference in surface 
tension between the fat and the liquid in which it is suspended, 
and thus promote its readier separation. This effect has been 
found to be heightened by the presence of a small amount of 
hydrochloric acid. 

The test-bottles have a capacity of about 30 c.c. and are 
provided with a graduated neck, each division of which repre- 
sents 0.1 per cent, by weight of butter fat. 

15 c.c. of the milk are measured into the bottle, 3 c.c. of a 
mixture of equal parts of amyl alcohol and strong hydro- 
chloric acid added, mixed, the bottle filled nearly to the neck 
with concentrated sulfuric acid, and the liquids mixed by 
holding the bottle by the neck and giving it a gyratory mo- 
tion. The neck is now filled to about the zero point with a 
mixture of sulfuric acid and water prepared at the time. It 
is then placed in the centrifugal machine, which is so arranged 
that when at rest the bottles are in a vertical position. If only 
one test is to be made, the equilibrium of the machine is main- 
tained by means of a test-bottle, or bottles, filled with a mixture 



204 FOOD ANALYSIS 

of equal parts of sulfuric acirl and water. After rotation for 
from one to two minutes, the fat will collect in the neck of the 
bottle and the percentage may be read off. It is convenient to 
use a pair of dividers in making the reading. The legs of these 
are placed at the upper and lower limits respectively of the fat, 
allowance being made for the meniscus; one leg is then placed 
at the zero point and the reading made with the other. Ex- 
perience by analysts in various parts of the world has shown 
that with properly graduated bottles the results are reliable. 
As a rule, they do not differ more than o.i per cent, from those 
obtained by the Adams process, and are generally even closer. 

For great accuracy, the factor for correcting the reading on 
each of the bottles should be determined by comparison with 
the figures obtained by the Adams or other standard process. 

Cream is to be diluted to exactly ten times its volume, the 
specific gravity taken, and the liquid treated as a milk. Since 
in the graduation of the test-bottles a specific gravity of 1.030 
is assumed, the reading must be increased in proportion. 

A more accurate result may be obtained by weighing in the 
test-bottle about 2 c.c. of the cream and diluting to about 15 c.c. 
The reading obtained is to be multiplied by 15.45 and divided 
by the w^eight in grams of cream taken. 

The mixture of fusel oil and hydrochloric acid seems to be- 
come less satisfactory when long kept. It should be clear and 
not very dark in color. It is best kept in a bottle provided with 
a pipet which can be filled to the mark Ijy dipping. Rigid 
accuracy in the measurement is not needed. 

See also Cochran''s method under ''Condensed Milk." 

Calculation Methods. — Several investigators have proposed 
formulae by which when any two of the data, specific gravity, 
fat, and total solids, are known, the third can be calculated. 
These vary according to the method of analysis employed. 
That of Hehner and Richmond, as corrected by Richmond, 
was deduced from results l)v the Adams method of fat extrac- 



MILK AND MILK PRODUCTS 205 

tion, and has been found to be the most satisfactory. It is as 
follows : 

T = 0.25 G + 1.2 F + 0.14; 

in which T is the total solids, G the last two figures of the specific 
gravity (water being 1000), and F the fat. A table based upon 
this formula is annexed. 

A formula has been devised by Richmond by which the lac- 
tose and proteids may be calculated (approximately), the specific 
gravity, fat, total solids, and ash being known. Thus: 

P^2.8T + 2.5A — 3.33 F- 0.7 -g-; 

in which P is the proteids, T the total solids, A the ash, F the 
fat, D specific gravity (water at 15.5° being taken as i), and 
G 1000 D — 1000. 

The difference between the total solids and the fat, proteids, 
and ash gives the lactose. In this formula it has been assumed 
that everything that is not fat, proteids, or ash, is milk-sugar, 
an assumption which is not strictly correct, and which intro- 
duces a small error. Another slight error is introduced by the 
fact that the ash in milk is not the same as the salts existing 
in the milk. 

Total Proteids. — For practical purposes the total pro- 
teids are best estimated by calculation from the total nitrogen 
obtained by the Kj eld ahl- Gunning method. Milk contains, 
however, a sensible proportion of non-proteid nitrogen. Ac- 
cording to Munk, this may range, in cow's milk, from 0.022 
to 0,034 per cent., and from 0.014 to 0.026 per cent, in human 
milk. By these figures, the average proteid nitrogen in cows' 
milk would be 94 per cent., and in human milk 91 per cent., 
of the total nitrogen. 

The determination of total nitrogen as recommended by tlic 
A. O. A. C. is to place in the digestion flask a known weight (about 
5 grams) of the sample and proceed, without evaporation, as 



2o6 



FOOD ANALYSIS 



Q 

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PQ 
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f) ro fO 



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u-i oo 
VO l~^ 



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VO 
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0\ IH 

t^ Ov 



ro <"0 fO ro fO fO 



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CM 



O «-« 



to 



VO 

to 



Ov 



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CM 






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ON 
CM 



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VO 



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On cm 
VO 00 



C7v 



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M M tH (M 



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0\ 
VO 






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0\ CM 






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NH w »- IH M CM 



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MILK AND MILK PRODUCTS 207 

described on page 33. The best factor for converting nitrogen 
to proteids is 6.38. 

Ritthausen Method. — This method depends on precipitation 
by copper sulfate and sodium hydroxid. It is apphcable only 
to fully developed milks; the proteids of colostrum and whey 
are only partially precipitated. The reagents are given on 
page 113. 

10 grams of milk are placed in a beaker, diluted with 100 
c.c. of distilled water, 5 c.c. of copper sulfate solution added, 
and thoroughly mixed. The sodium hydroxid solution is then 
added drop by drop, with constant stirring, until the precipitate 
settles quickly and the liquid is neutral, or at most very feebly 
acid. An excess of alkali will prevent the precipitation of some 
of the proteids. 

The reaction should be tested on a drop of the clear liquid, 
withdrawing it by means of a rod, taking care not to include 
any solid particles. When the operation is correctly performed, 
the precipitate, which includes the fat, settles quickly, and car- 
ries down all of the copper. It is washed by decantation with 
about 100 c.c. of water, and colleced on a filter (previously dried 
at 130° and weighed in a weighing bottle). The portions ad- 
hering to the sides of the beaker are dislodged with the aid of a 
rubber-tipped rod. The contents of the filter are washed with 
water until 250 c.c. are collected, which are mixed and reserved 
for the determination of the sugar as described below. The 
water in the precipitate is removed by washing once with strong 
alcohol, and the fat by six or eight washings with ether. An 
extraction apparatus may be used for this purpose. The wash- 
ings being received in a weighed flask, the determination of 
the fat may be made by evaporating the ether, with the usual 
precautions. 

The residue on the Jiltcr, which consists of the proteids in 
association with copper hydroxid, is washed with absolute 
alcohol, which renders it more granular, and then dried at 130° 



2o8 FOOD ANALYSIS 

in the air balh. ll is weighed in a weighing bottle, transferred to 
a porcelain crucible, incinerated, and the residue again weighed. 
The weight of the filter and contents, less that of the filter 
and residue after ignition, gives the weight of the proteids. 
The results by this method are slightly high, since copper hy- 
droxid does not become completely converted into copper oxid 
at 130.° 

Richmond & Boseley have modified the process by diluting 
the milk to 200 c.c, adding a little phenophthalein, and neu- 
tralizing any acidity by the cautious addition of dilute sodium 
hydroxid solution, then adding from 2.0 to 2.5 c.c. of the copper 
sulfate solution. The precipitate is allowed to settle, washed, 
and estimated as above. 

Casein and Albumin. — The most accurate separation of 
casein and albumin is made by Sebelein's method, as follows: 
20 c.c. of the sample are mixed w^ith 40 c.c. of a saturated solu- 
tion of magnesium sulfate and powdered magnesium sulfate 
stirred in until no more will dissolve. The precipitate of casein 
and fat, including the trace of globulin, is allow^ed to settle, fil- 
tered, and washed several times with a saturated solution of 
magnesium sulfate. The filtrate and washings are saved for 
the determination of albumin. The filter and contents are 
transferred to a flask and the nitrogen determined by the 
method described above. The nitrogen so found, multiplied 
by 6.38, gives the casein. 

The filtrate and w^ashings from the determination of casein 
are mixed, the albumin precipitated by Almett's tannin reagent, 
filtered, and the nitrogen in the precipitate determined as above. 
The same factor is used. 

Almen's reagent is prepared by dissolving 4 grams of tan- 
nin in 190 c.c. of 50 per cent, alcohol and adding 8 c.c. of acetic 
acid of 25 per cent. 

In a mixture of milk and whey (prepared with rennet) in 
about equal parts, Richmond and Boseley found about 0.3 



MILK AND MILK PRODUCTS 209 

per cent, of albumoses not precipitated by the copper sulfate 
nor by magnesium sulfate, but precipitable, along with the 
albumin, by a solution of tannin. The separation may be 
effected by diluting the filtrate from the magnesium sulfate pre- 
cipitation, acidifying slightly with acetic acid, and boiling, 
when the albumin will be coagulated and precipitated. The 
albumoses may be separated by filtering the solution and pre- 
cipitating with tannin solution. The precipitated proteids are 
best estimated by determining the nitrogen in the moist preci- 
pitate. The separation of the proteids may be effected, though 
less accurately, by the use of acetic acid, as recommended by 
Hoppe-Seyler and Ritthausen. 

The following are A. O. A. C. methods: 

1. Provisional Method for the Determination of Casein in 
Cows^ Milk. — The determination should be made when the 
milk is fresh. When it is not practicable to make the deter- 
mination within 24 hours, add one part of formaldehyde to 
2500 parts of milk and keep in a cool place. lo grams of the 
sample are diluted with about 90 c.c. of water at between 40° 
and 42°, 1.5 c.c. of a solution containing 10 per cent, of acetic 
acid by weight added, allowed to stand for five minutes, 
washed three times by decantation, pouring the w^ashings 
through a filter, and the precipitate transferred completely to 
the filter. If the filtrate is not clear at first, it will generally 
become so in two or three filtrations, after which the washing 
can be completed. The nitrogen in the washed precipitate - 
and filter is determined by the Kjeldahl-Gunning method. 
The nitrogen, multiplied by 6.38, gives the casein. 

In working with milk which has been kept with preservatives, 
the acetic acid should be added in small portions, a few drops 
at a time with stirring, and the addition continued until the 
liquid above the precipitate becomes clear or nearly so. 

2. Provisional Method jor the Determination oj Albumin in 

Milk. — The filtrate obtained in the above operation is neutral 
19 



2IO FOOD AXALVSIS 

izi'd with sodium hydroxid, 0.3 c.c. of the 10 per cent, solution of 
acetic acid added, and the mixture heated for 15 minutes. 
The precipitate is collected on a filter, washed, and the nitro- 
gen determined. 

We have found the following method satisfactory, avoiding 
the difficulty of washing the precipitate: 10 c.c. of the milk 
are mixed with saturated magnesium sulfate solution and the 
powdered salt added to saturation. The mixture is washed 
into a graduated measure with a small amount of the saturated 
solution, made up to 100 c.c. with the same solution, mixed, 
and allowed to stand until the separation takes place. As 
much as possible of the clear portion is drawn of! with a pipet 
and passed through a dry filter. An ali(jU()t portion of the 
filtrate is taken, the albumin i)recipitated by a solution of tan- 
nin, and the nitrogen in the precipitate determined as above. 

The casein is found by subtracting the figure for albumin 
from that for total proteids. 

Lactose. — Soxhlet's method, adopted by the A. O. A. C, is 
as follows: 25 c.c. of the sample in a 500 c.c. flask are diluted 
with 400 c.c. of water and 10 c.c. of copper sulfate solution 
(34.639 grams crystallized copper sulfate in 500 c.c.) and 8.8 
c.c. -^ sodium hydroxid solution added. (The mixture should 
still have an acid reaction and contain copper in solution. If 
this is not the case, the experiment must be repeated, using a 
little less of the alkah.) The flask is filled to the mark with 
water, shaken, and the liquid passed through a dry filter, 50 
c.c. of the mixed copper reagent (page 113) are heated to 
brisk boiling in a 300 c.c. beaker, 100 c.c. of the liltrate obtained 
as above added, and boiling continued for six minutes; the 
liquid then promptly filtered, and treated according to methods 
given on pages 114 to 117. The amount of lactose is calculated 
by the table on page 211 from the copper obtained by table. 
The figures for weights of copper between any two data given 
in the table mav be calculated with suflicient accuracy for 



MILK AND MILK PRODUCTS 



211 



practical purposes by allowing 0.0008 gram of lactose for each 
o.ooi gram of copper. 



Copper. 


Lactose. 


Copper. 


Lactose. 


Copper. 


Lactose. 


0. 100 


0.072 


0.205 


0.151 


0305 


0.228 


0.105 


0.075 


0.210 


0.154 


0.310 


0.232 


O.I 10 


0.079 


0.215 


0.158 


0-315 


0.236 


0.115 


0.083 


0.220 


0.162 


0.320 


0.240 


0.120 


0086 


0.225 


0.165 


0-325 


0.244 


0.125 


' 0.090 


0.230 


0.169 


0.330 


0.248 


0.130 


0.094 


0-235 


0.173 


0.335 


0.252 


0-135 


0.097 


0.240 


0.177 


0.340 


0.256 


0.140 


O.IOI 


0.245 


0.181 


0.345 


0.260 


0.145 


0.105 


0.250 


0.185 


0.350 


0.264 


0.150 


0.109 


0.255 


0.189 


0.355 


0.268 


0-155 


0. 112 


0.260 


0.192 


0.360 


0.272 


0. 160 


O.I 16 


0.265 


0.196 


0.365 


0.276 


0.165 


0.120 


0.270 


0.200 


0.370 


0.280 


0.170 


0.124 


0.275 


0.204 


0-375 


0.285 


0-175 


0.128 


0.280 


0.208 


0.380 


0.289 


0.180 


0.132 


0.285 


0.212 


0.385 


0.293 


0.185 


0.134 


0.290 


0.216 


0.390 


0.298 


0.190 


0.139 


0.295 


0.221 


0-395 


0.302 


0.195 


0.I4I 


0.300 


0.224 


0.400 


0.306 


0.200 


0.147 











Lactose may be determined by the polarimeter after removal 
of the fat and proteids, which is best effected, as recommended 
by Wiley, by a mercuric nitrate solution, prepared by dissolving 
mercury in twice its weight of nitric acid of 1.42 sp. gr. and add- 
ing to the solution five volumes of water. The A. O. A. C. 
optical method is as follows: 

For polarimeters reading to 100 for 26.048 grams sucrose 
(corresponding to 32.98 grams lactose), measure, in c.c, the 
amount obtained by dividing double this (/. e., 65.96) by the 
specific gravity, add 10 c.c. mercuric nitrate solution, make up 
to 102.6 c.c, shake, filter through a dry filter and examine in a 
200 mm. tube. Half the observed reading will be the per- 



212 FOOD ANALYSIS 

centage of lactose. For example, if the specific gravity of the 
milk is 1.030, the amount taken will be 65.96 -4- 1.030=64 c.c. 

The allowance for volume of precipitate by making up to 
102.6 c.c. is not accurate, except wdth closely-skimmed milks. 

The correction may be made more closely by calculating 
the actual volume of the precipitate by multiplying the fat-per- 
centage by 1.075 (average specific volume of fat) and the 
proteid-percentage by 0.8 (average specific volume of coagulated 
proteids), deducting the sum of these products from 100 c.c. 
and correcting the observed reading by proportion. For 
ordinary milk, the volume of the proteids from 65.96 grams may 
be taken at 1.68 c.c. Supposing the sample to contain 4.0 per 
cent, of fat and the polarimetric reading to be 10, the calcula- 
tion would be thus : 

65.96 X 0.04 = 2.63 Amount of fat in milk taken 

2.63 X 1.075 = 2.82 c.c. Volmne of fat in precipitate 

1.68 c c. Est. vol. of proteids in precipitate 

4.50 c.c. Total volume of precipitate 
100 — 4.50 = 95.5 c.c. Actual volume of liquid. 
100 : 95.5 : : 10 : 9.55 9.55 h- 2 = 4.75, per cent, lactose 

The employment of a factor for correcting for the volume of 
precipitate may be avoided by Scheibler's method of "double 
dilution" (see page 21), in which two solutions of different vol- 
ume are compared. The following is a summary of the method 
given by Wiley & Ewell : For polarimeters adapted to a normal 
weight of 26.048 sucrose, 65.82 grams of milk are placed in 
a 100 c.c. flask, 10 c.c. of the acid mercuric nitrate added, the 
flask filled to the mark, the contents well mixed, filtered, and 
a reading taken. A similar quantity of the milk is placed 
in a 200 c.c. flask and treated in the same way. The true 
reading is obtained by dividing the product of the two readings 
by their difference. If the observations are made in a 200 mm. 
tube the percentage is half the true reading. 

The instrument should be accurate, and great care taken in 



MILK AND MILK PRODUCTS 213 

the work, or the results will be less satisfactory than by the 
method first described, in which an allowance is made for the 
volume of the precipitate. 

Birotation. — When freshly dissolved in cold water, lac- 
tose shows a higher rotation than that given above. By stand- 
ing, or immediately on boiling, the rotatory power falls to the 
point mentioned. In preparing solutions from the solid, there- 
fore, care must be taken to bring them to the boiling- 
point previous to making up to a definite volume. This precau- 
tion is unnecessary when operating on milk. 

Adulterations. — The addition of water to milk is usually 
detected by the diminution in the amount of solids. The ad- 
dition of water decreases the specfic gravity, while abstraction 
of, fat increases it. 

Several observers have found that the whey (milk-serum) 
obtained by a routine method is of constant composition and 
that by its specific gravity or refractive index, watering may be 
detected. Woodman^* recommends the following method for 
obtaining a standard whey: loo c.c. of the sample are mixed 
with 2 c.c. of dilute acetic acid (sp. gr. 1035, containing 25 per 
cent, acetic acid), the vessel covered with a watch-glass and heated 
in the water-bath for 20 minutes, at 70.° It is then placed 
in ice- water for 10 minutes, and the solution filtered. The 
specific gravity may be taken under the usual precautions, or; 
as suggested by Leach, ^^ the refractive index may be observed. 
The routine of precipitation must be closely followed, as the 
amount of proteids precipitated differs with the method. The 
total solids and polarimetric reading of the whey might be taken 
as additional data. The latter figure will be somewhat less 
than that due to the milk-sugar, as the proteids in solution are 
levorotatory. 

The following are some of the limits recorded, but analysts 
should make determinations on samples of known composition. 

For the Zeiss immersion refractometer, an instrument of 
special construction, Leach & Lythgoe''^ consider 39 as the 



214 FOOD ANALYSIS 

lowest permissible reading. This corresponds to 1.3424 on the 
x\bbe refractometer. 

From unwatered whole milk, Leach obtained a serum of sp. 
gr. 1.0287; from unwatered centrifugal skimmed milk, a serum 
of 1.0296, at 15°. 

\'ieth has pointed out that in normal milks the ratio sugar: 
proteids : ash =13:9:2 exists, and a determination of these 
ratios may aid in the attempt to distinguish genuine but ab- 
normal milks from watered milks. In the case of a watered 
milk the proportion would remain unchanged, but in abnormal 
milk it has been found to vary. 

Richmond states that the determination of the amount of 
water that has been added to milk is best calculated from the 
figures obtained by adding the difference between the specific 
gravity of the sample and 1000 to the figure representing the 
percentage of the fat. Thus, if a milk have the specific gravity 
of 1029.2 and contain 3.27 per cent, of fat, the figure from which 
the water is calculated is 29.2 -f 3.27 = 32.47. The mean figure 
from unadulterated milks was found to be 36.0, but 34.5 is con- 
sidered to be a safer limit. Accepting this figure, the percen- 
tage of added water in the sample given above will be found by 
the proportion 34.5 : 23.47 : 100 :: 94.1, /. c, the sample contains 
5.9 per cent, of water. Experiments on milks which had been 
diluted with known proportions of water showed that this method 
of calculating the added water gave nearer approximations to 
the truth than by calculating from the figure for non-fatty solids. 

It is stated that the watering of milk can be detected by the 
lowering of the freezing-point. The freezing-point of whole 
milk ranges from — 0.55 to — 0.57. Bomstein''^ claims that as 
little as 5 per cent, added water can be detected by this method. 
The special apparatus devised for these determinations (known 
as "cryoscopy") must be used, and the data must be determined 
by each observer in order to be safely comparable. 

For ordinary milk control it will suftice to take the specific 



MILK AND MILK PRODUCTS 21 5 

gravity by the lactodensimeter (see page 107) and the fat by the 
Leffmann-Beam method. From the figures thus obtained the 
total sohds can be ascertained from the table or Richmond's 
slide- rjLile. 

Coloring and Thickening Agents. — Several instances of the 
use of brain-matter, dextrin, and gelatin have been recorded. 
It is also stated that sugar, salt, and starch have been added. 
Thickening agents of pectinous nature are now commercial 
articles. For some information concerning them see under 
''Agar." A solution of 10.5 per cent, sugar and 5.5 per cent. 
calcium oxid has been sold under the name "Grossin" for 
thickening cream. It could, of course, be at once detected by 
the increased polarimetric reading and increased ash. Starch 
will be easily detected by the iodin test. Coloring matters are 
used to conceal inferiority in quality. 

At the present time preparations of annatto, turmeric, and 
some coal-tar colors are used, especially the latter. Caramel 
is occasionally used, saffron and carotin but rarely. Annatto 
may be detected by rendering the sample slightly alkaline by 
acid sodium carbonate, immersing a slip of filter-paper, and 
allowing it to remain overnight. Annatto will cause a reddish- 
yellow stain on the paper. 

Leys gives the following method for detecting annatto: 
50 c.c. of the sample are shaken with 40 c.c. of 95 per cent, 
alcohol, 50 c.c. of ether, 3 c.c. of water, and 1.5 c.c. of am- 
monium hydroxid solution (sp. gr. 0.900), and allowed to stand 
for 20 minutes. The lower layer, which in presence of annatto 
will have a greenish-yellow tint, is tapped off and gradually 
treated with half its measure of 10 per cent, solution of sodium 
sulfate, the separator being inverted without shaking, after 
each addition. By this treatment the casein separates in flakes 
which conglomerate and rise to the surface, when the adjacent 
liquid is tapped off, strained through wire gauze, and placed in 
four test-tubes. To each of these amyl alcohol is added, and 



2l6 FOOD ANALYSIS 

tlu" lubes shaken and immersed in cold water, which is gradually 
raised to 80°. This causes the emulsion to break u\), and the 
alcohol, holding the annatto in solution, to come to the surface. 
The alcoholic layer is separated from the lower stratum, evapo- 
rated to dryness, and the residue dissolved in warm water con- 
taining a little alcohol and ammonium hydroxid. A bundle of 
white cotton fibers is introduced and the liquid evaporated 
nearly to dryness on the water-bath. The fiber, which is colored 
a pale yellow, even with pure milk, is washed and immersed 
in a solution of citric acid, when it will be immediately colored 
rose-red if the milk contained annatto. Saft'ron, turmeric, and 
the coloring-matter of marigolds do not give a similar reaction. 

Coal-tar colors may often be detected by the wool-test (p. 
64), but Lythgoe has devised the following method, which he 
finds very satisfactory: 15 c.c. of the sample are mixed in a 
porcelain basin with an equal volume of hydrochloric acid (sp. 
gr. 1.20), and the mass shaken gently so as to break the curd 
into coarse lumps. If the milk contains an azo-color, the curd 
will be pink ; with normal milk the curd will be white or yellow- 
ish. (See next page; also under "Butter.") 

Salt and cane-sugar are occasionally added to milk that has 
been diluted with water. The former is detected by the taste, 
the increased proportion of ash and of chlorin. Cane-sugar 
may be detected, if in considerable quantity, by the taste. 
Cotton devised the following test: 10 c.c. of the sample are 
mixed with 0.5 gram of powdered ammonium molybdate, and 
10 c.c. of dilute hydrochloric acid (i to 10) are added. In a 
second tube 10 c.c. of milk of known purity or 10 c.c. of a 6 per 
cent, solution of milk-sugar are similarly treated. The tubes 
are then placed in the water-bath and the temperature gradually 
raised to about 80°. If sucrose be present, the milk will as- 
sume an intense blue color, while genuine milk or milk-sugar 
remains unaltered unless the temperature be raised to the boil- 
ing-point. According to Cotton, the reaction is well marked 



MILK AND MILK PRODUCTS 



217 



in the presence of as little as i gram of sucrose to a liter of the 
milk, and 6 grams and over per liter are usually found in adul- 
terated samples. (See also page no.) 

The quantitative determination is made by the methods 
described in connection with condensed milk. 

General Method for Colors in Milk. — Leach^^ has devised a 
general method for detecting colors in milk. 150 c.c. of the 
sample are coagulated in a porcelain basin, with the addition 
of acetic acid and heating, and the curd separated from the 
whey. The curd will often collect in a mass; but if this does 
not occur, it must be freed from whey by straining through 
muslin. The curd is macerated for several hours in a closed 
flask, with occasional shaking, with ether to extract fat. An- 
natto will also be removed by it. The ether and curd are 
separated and treated as follows : 



The ether is evaporated, the residue 
mixed with a little weak solution 
of sodium hydroxid, and passed 
through a wet filter; and when this 
has drained, the fat is washed off 
and the paper dried. An orange 
tint shows annatto, which may be 
confirmed by a drop of solution of 
stannous chlorid, which makes a 
pink spot. 



If the curd be colorless, no foreign 
coloring-matter is in it; if orange 
or brown, it should be shaken with 
strong hydrochloric acid in a test- 
tube. 



If the mass turns 
blue gradually, 
caramel is pro- 
bably present. 
The wh e y 
should be ex- 
amine d for 
caramel (see 
page 125). 



If the mass turns 
pink at once, an 
azo-color is indi- 
cated. 



Gelatin. — Stokes detects the presence of gelatin in cream or 
milk as follows: 10 c.c. of the sample, 20 c.c. of cold water, 
and 10 c.c. of acid mercuric nitrate solution (page 211) are 
mixed, shaken vigorously, allowed to stand for five minutes, and 
filtered. If much gelatin be present, it will be impossible to 
get a clear filtrate. A portion of the filtrate is mixed with an 
equal bulk of saturated aqueous solution of picric acid. If any 
gelatin be present, a yellow precipitate will be immediately 



20 



2l8 FOOD ANALYSIS 

produced. Picric acid will detect the presence of one part of 
gelatin in 10,000 parts of water. 

Antiseptic substances are largely used, especially in the 
warmer season, as a substitute for refrigeration. Alany of 
these are sold under proprietary names which give no indica- 
tion of their composition. Preparations of boric acid and 
borax were at one time the most frequent in use, but lately for- 
malin, a 40 per cent, solution of formaldehyde (methyl alde- 
hyde), has come into favor. Sodium benzoate is now in common 
use as a preservative of cider, fruit-jellies, and similar articles, 
and may, therefore, be found in milk. Salicylic acid is not so 
much employed as in former years. Sodium carbonate is oc- 
casionally used to prevent coagulation due to slight souring. 
A mixture of boric acid and borax is more efficient than either 
alone. The quantity generally used is equivalent to about 0.5 
gram of boric acid per liter. Formaldehyde is the most effi- 
cient antiseptic. In the proportion of 0.125 gram to the liter, 
it will keep milk sweet for a week. 

Formaldehyde. — The presence of this body may sometimes 
be detected by the odor developed on warming the milk. 
Hehner's test depends upon the fact that when milk containing 
it is mixed with sulfuric acid containing a trace of ferric salt a 
blue color appears. Richmond & Boseley showed that the 
delicacy of the test is much increased by diluting the milk 
with an equal bulk of water and adding sulfuric acid of 90 to 
94 per cent., so that it forms a layer underneath the milk. 
Under these conditions, milk, in the absence of formaldehyde, 
gives a slight greenish tinge at the junction of the two liquids, 
while a violet ring is formed when formaldehyde is present even 
in so small a quantity as i part in 200,000 of milk. The color 
is permanent for two or three days. In the absence of formalde- 
hyde, a brownish color is developed after some hours, not at 
the junction of the two liquids, but lower down in the acid. 

The phenylhydrazin and phloroglucol tests described on 



MILK AND MILK PRODUCTS 219 

page 83 are applicable, but the former gives a grayish green 
liquid instead of the blue given with ordinary formaldehyde 
solutions. 

Hydrochloric acid containing a small amount of ferric chlorid 
gives a characteristic violet with quantities of formaldehyde 
not over one part per 1000. The test is applied by heating i 
c.c. of the sample with 4 c.c. of strong hydrochloric acid. If a 
yellow liquid is formed, the sample should be diluted two or 
three times and the test repeated. Hydrochloric acid often 
contains sufficient ferric chlorid to give the test. The addition 
of 0.25 gram of ferric chlorid to 1000 c.c. of pure acid will be 
sufficient. 

Hehner also gives the following test : Some of the milk is 
distilled and to the distillate one drop of a dilute aqueous so- 
lution of phenol is added and the mixture poured on strong 
sulfuric acid contained in a test-tube. A bright crimson zone 
appears at the line of contact. This color is readily seen with 
I part of formaldehyde in 200,000 of water. If there is more 
than I part in 100,000, there is seen above the red ring a 
white, milky zone, while in stronger solutions a copious white 
or slightly pink, curdy precipitate is obtained. 

The reaction succeeds only when carried out as described 
above; the phenol must first be mixed with the solution to be 
tested, and the mixture poured upon the sulfuric acid. Only 
a trace of phenol must be used, and if it be first dissolved in 
the acid and the formaldehyde solution added, no color is ob- 
tained. The precipitate might be utilized for the determina- 
tion of the strength of dilute formalin solutions. 

The rate at which formaldehyde disappears from milk has 
been investigated by Hehner, who found that at the end of a 
week none could be detected in a sample to which had been 
added i part in 100,000; after two weeks none could be de- 
tected in a sample of i part in 50,000; after three weeks only 
a trace could be detected with i part in 25,000. 



2 20 FOOD ANALYSIS 

For the delerminalion of the formaldehyde, the sample must 
be distilled, but only an aliquot portion can be obtained. B. H. 
Smith found that if loo c.c. of milk be mixed with i c.c. of 
dilute sulfuric acid (i : 3), one-third of the formaldehyde present 
will pass over the first 20 c.c. of distillate. The distillation of 
milk is troublesome owing to bumping and frothing. Smith 
found that it could be conducted satisfactorily in a 500 c.c. 
Kjeldahl flask with the evaporating burner shown on page 

52. 

Sodium Carbonate. — The following test is due to Schmidt. 

10 c.c. of the milk are mixed with an equal volume of alcohol, 
and a few drops of a i per cent, solution of rosolic acid added. 
Pure milk shows merely a brownish-yellow color, but in the 
presence of sodium carbonate a more or less marked rose-red 
appears. The delicacy of the test is enhanced by making a 
comparison cylinder with the same amount of milk known to 
be pure. If the salt is present in considerable amount, it may 
be detected by the increase in the ash, its marked alkalinity and 
effervescence with acid. 

Ahrastol. — i c.c. of acid mercuric nitrate solution (page 211) 
is added to 20 c.c. of milk. A yellow tint indicates abrastol. 
The delicacy of the test may be increased by comparison with 
an untreated portion of the sample. The absence of other 
preservatives should be assured. The extraction method given 
on page 86 is not always satisfactory with milk. 

Preservation of Milk-samples. — Formaldehyde is now gen- 
erally used; 0.05 per cent, will keep milk for a month and 
larger proportions for an indefinite period. 

Bevan has, however, noted the fact that the total solids of 
milk containing formaldehyde are always higher, and that the 
increase is much greater than can be accounted for, even as- 
suming that all the formaldehyde remains in the residue. 

Detection of Boiled Milk. — Dupouy proposed the following 
method: A few drops of a solution of 1-4 diamidobenzene in 



MILK AND MILK PRODUCTS 221 

water are added to 5 c.c. of the sample, and then a few drops 
of hydrogen dioxid solution. Raw milk gives a blue color; 
milk that has been heated to over 79° gives no color. The 
splution of diamidobenzene must be freshly prepared. Rosier 
has found that 1-3- diamidobenzene will serve, and that if the 
blue milk be shaken with amyl alcohol, the blue color passes 
into the latter and is more stable. These tests are applicable 
for distinguishing between pasteurized and sterilized milks, 
as the reactivity of milk is lost between 75° and 80°. 

Faber has shown that raw milk may be distinguished from 
boiled milk or milk that has been heated above 75° by the fact 
that such treatment coagulates or alters the albumin so that if 
the liquid be saturated with magnesium sulfate, the albumin 
is Separated along with the albumin casein. 

Richmond & Boseley recommend the following methods to 
distinguish new milk from milk which has been sterilized: 

(a) 100 c.c. of the sample are allowed to stand in a gradu- 
ated cylinder for six hours at 15.5° and the percentage of cream 
noted. If less than 2.5 per cent, of cream has risen for each i 
per cent, of fat in the milk, the milk may be considered suspi- 
cious; if the quantity of cream falls decidedly below 2 per cent. 
for each i per cent, of fat, it is probable that sterilized milk is 
present. 

(h) The albumin is determined by means of magnesium 
sulfate. If less than 0.35 per cent, is found, sterilized milk 
may be considered to be present. 

(c) The milk-sugar is determined by the polarimeter, and 
also gravimetrically, in duplicate. If the difference between 
the two estimations be more than 0.2 per cent., it will be cor- 
roborative evidence of the presence of sterilized milk. It is 
doubtful whether a proportion of sterilized milk much below 
30 per cent, can be detected. 

The following figures, by Stewart, show the percentage of 
soluble albumin found in milk raised to various temperatures: 



222 FOOD ANALYSIS 















Soluble Albumin in 


Soluble Albumi.v in 


TlMK 


OF 


Heating. 


Fresh Milk. 


Heated Milk. 


lO 


ininulcs 


at 60° 


0.423 


0.418 


30 










60° 


0-435 


0.427 


10 










65° 


0-395 


0.362 


30 










65° 


0-395 


°-333 


10 










70° 


0.422 


0.269 


30 










70° 


0.421 


0-253 


10 










75° 


0.380 


0.07 


30 










75° 


0.380 


0.05 


10 










80° 


0-375 


none. 


30 










80° 


0-375 


none. 



CONDENSED AIILK 

The form of condensed milk called *' evaporated cream" con- 
sists merely of whole milk concentrated to about two-fifths 
of its bulk, but most condensed milks contain a considerable 
amount of cane-sugar. These samples represent, usually, 
whole milk concentrated to about one-third or two-sevenths 
of its original volume. A small amount of invert-sugar may 
be present. Portions of the lactose may crystallize from con- 
densed milk, and when solutions are prepared for analysis, 
abnormal polarimetric reading will result unless the liquid 
stands for some hours or is heated for a short time to 100°. The 
most common defect in condensed milks is deficiency in fat, 
due to preparation from closely-skimmed milks. Preserva- 
tives (other than cane-sugar) and coloring-matters are rarely 
used, nor is it likely that foreign fats will be present. 

ANALYSES OF COMMERCIAL CONDENSED MILKS 



Total 
Solids. 


Fat. 


Proteids. 


Lactose. 


Sucrose. 


Ash. 


Analyst. 


367 


10.5 


9-7 


14.2 


none 


2.1 


Pearmain and Moor 


31.2 


9.6 


9.2 


10.9 


none 


1-5 


F. J. Aschman 


28.1 


8.8 


8-5 


9.8 


none 


1.8 


F. J. Aschman 


78.4 


9-3 


9.1 


134 


40.4 


2.0 


F. J. Aschman 


74.2 


9.0 


9-3 


10.2 


43-7 


1.9 


F. J. Aschman 


70.9 


1.4 


11.4 


14.6 


41.9 


1.6 


Pearmain and Moor 



The sucrose in the last sample was determined by difference. 



CONDENSED MILK 223 

The analysis of unsweetened condensed milks is conducted 
as with ordinary milk, the sample having been previously 
diluted with several times its weight of water heated to boil- 
ing, cooled, and made up to a definite volume. The fat may 
be readily estimated by the L-B. process. 

The full analysis of sweetened condensed milk is difficult, 
and many of the published figures are erroneous. The cane- 
sugar interferes with the extraction of the fat by solvents. The 
same difficulty occurs in the analysis of some prepared infant- 
foods, such as mixtures of milk with malt and glucose. 

For the general operations, a portion of the well-mixed con- 
tents of a freshly opened can should be accurately weighed, 
diluted with a known amount of water, and well mixed, from 
which mass the portions for analysis may be taken and the re- 
sults calculated to the original sample. 50 grams mixed with 
150 c.c. of water will be a convenient quantity. For the polar- 
imetric determination of lactose, a special procedure will be 
necessary; but for determination of solids, ash, total proteids, 
and total reducing sugars, the examination may be made as 
with ordinary milk upon this diluted sample. 

Fat. — The Adams method is not satisfactory under ordinary 
conditions, owing to the sucrose. Geisler substituted petro- 
leum spirit or a mixture of this with anhydrous ether, extracting 
for five hours. Bryant has obtained better results with carbon 
tetrachlorid, which is, moreover, safer. 

Some analysts have advised the extraction of the fat from 
the precipitate obtained with copper sulfate (see page 207). 
This is collected on fat-free filter paper (hardened paper will 
answer), washed and dried. The folded filter is placed on a 
fat-free thimble and extracted with carbon tetrachlorid for 
several hours. 

The Werner-Schmid method may be employed, but the fat 
is apt to be contaminated with caramel. It should be dissolved 
in anhydrous ether, by which the caramel will be left adher- 



224 FOOD ANALYSIS 

ing to ihc glass; and after washing this with a little more ether, 
it should be dried and weighed and the fat determined by dif- 
ference. 

The estimation of fat by centrifugal method is seriously 
impeded by the carbonization of the sucrose, and various 
methods have been proposed for overcoming this difficulty. 
Leach devised the following method, which he finds to be more 
trustworthy than ordinary- extractions with solvents. Leach 
applied the process to a centrifugal method not identical with 
the one described on page 203, but this is not important: 

25 c.c. of diluted material are measured into the test-bottle, 
water added sufficient to fill it to the beginning of the stem, 
and then 4 c.c. of the copper sulfate solution used for sugar 
determination, the mixture allowed to stand for a few minutes, 
then shaken well, and the precipitate settled by whirling the 
bottle in the machine. The supernatant liquid is drawn off. 
The precipitate is washed twice with water by the same method, 
settling the precipitate in each case by the use of the centrifuge, 
taking care that the mass is well stirred w^ith the water before 
each whirling. After the second washing, about 15 c.c. of 
water are put in, the precipitate stirred up, the amyl alcohol 
mixture added, then the sulfuric acid, as directed on page 203, 
the mixture whirled, and the fat measured. The percentage 
of fat will be that based on the 25 c.c. used, and the amount in 
the original sample may be calculated from the dilution. 

Cochran's method. — This is based on the solution of the curd 
by the DeLaval method and solution of the fat in ether. It may 
be applied by means of the L-B. bottles and centrifuge, or with 
a special flask (which does not require a centrifuge) devised by 
Cochran. If L-B. bottles are used, the reading must be multi- 
plied by 3, since only 5 c.c. of the sample are taken. The pro- 
cess is especially adapted to sweetened condensed milk and 
cereal foods containing fat. The fat of normal cereals can be 
accuratelv determined bv it. The curd is dissolved bv a mixture 



CONDENSED MILK 22$ 

of equal parts sulfuric acid and 80 per cent, acetic acid. This 
mixture may be made beforehand or the acids may be added 
in succession to the material in the bottle or flask. With the 
flask, all materials must be added through the side-tube. 

Ordinary milk is taken undiluted, but condensed milk is 
diluted. Sweetened condensed milk is diluted with 3 times its 
weight of water; unsweetened condensed with an equal weight 
of water. 

5 c.c. of the prepared sample are introduced into the flask 
by means of the side-tube, 5 c.c. of the acid mixture added slowly 
with shaking, taking care that the liquid does not get into the 
graduated tube. If the liquid becomes dark brown and free 
from lumps of undissolved curd, the flask is allowed to cool and 
4 c.c. of ether added (common ether will answer). If the mix- 
ture produced by the acid is lumpy, the flask is set in tepid 
water, heated gradually (not above 80°) and shaken gently until 
all flocculent matter is dissolved. Care must be taken not to 
continue this heating until masses of caramel are formed, as 
this will prevent correct results being obtained. 

When the flocculent matter has disappeared (the liquid will 
in any case show some turbidity from the emulsion of fat), the 
flask is cooled and ether added as noted above. The flask is 
well shaken to cause the ether to take up all the fat, taking care 
not to bring the liquid up into the graduated tube. When the 
fat is dissolved, the flask is placed in water at about 40°, kept 
still and the temperature raised slowly until all ether is vaporized, 
then rapidly until the boiling-point is reached, and this con- 
tinued until the solution ceases to bubble, and the fat forms a 
clear layer on the surface of the dark but clear acid solution. 
The flask should not be skaken while evaporating the ether. 
Water heated to nearly boiling is now run cautiously into the 
side-tube until the flask is three-quarters full. If any fat is in 
the side-tube, it may be removed by blowing gently into it. 
If the liquid is producing but few bubbles, more hot water should 



226 FOOD ANALYSIS 

1)L' run in until all the fat is within the limits of the graduation. 
If the bubbling is still violent when the tube is only three-quarters 
full, the lower half of the flask should be cooled by immersion 
in cold water, when the bubbling will nearly cease, and the fat 
may then be raised into the neck by adding more hot water. 
The flask may stand for a minute, if necessary to allows the fat 
column to unite, but it should be measured as soon as possible. 
The graduation is percentage of fat by w^eight, based on 5 c.c. 
of milk (say 5.16 grams). If the sample has been diluted, the 
reading must be increased by the factor of dilution. 

The process is easy of accurate operation and is especially 
adapted to materials that do not yield fat to common extraction 
methods. The special point is to avoid prolonged or excessive 
heating with the acid liquid, as this will produce lumps of partly 
carbonized matter. If these form, the operation must be dis- 
continued and the flask cleaned promptly. This lumpy ma- 
terial should be distinguished from a brown flocculent matter 
which rests between the acid and ether layer at the early part 
of the operation, but which disappears later. 

For the examination of malted cereals, 1.72 grams are taken 
and introduced by the side-tube, taking care that no more ma- 
terial adheres than can be washed into the flask by not more 
than 5 c.c. of water. The mass is mixed thoroughly by shaking, 
3 c.c. of the acid mixture are introduced and the process is 
carried out as described, taking especial care not to overheat. 
The volume of fat multiplied by 3 gives percentage. 

^lost malted cereals are easily treated by the method, but 
some contain insoluble cellular matter. With care, this will 
not interfere. Sometimes previous treatment with diluted sul- 
furic acid will render the material more tractable. 

The flasks should be cleaned promptly. The chromic-sul- 
furic mixture (see page 51) is the best. 

Sugars. — If regard is to be given to the presence of invert- 



CONDENSED MILK 227 

sugar, a special method must be followed. The processes 
first given consider lactose and sucrose only. 

Lactose. — The heating employed in the manufacture of con- 
densed milk may reduce the rotatory power of the sugar suf- 
ficiently to cause error in the polarimetric method. The reducing 
power with alkaline copper solutions is not seriously affected. 

Sucrose. — This determination may be made by difference; 
that is, subtracting the sum of the other ingredients from the 
total solids. This will serve for ordinary inspection purposes, 
since the amount present is almost always large, generally 
more than the total of milk-solids, and an error even of several 
per cent, does not affect the judgment as to the wholesomeness 
of the sample. Exact work requires, however, that the cane- 
sugar be determined directly, and several processes have been 
devised for the purpose. Sucrose exerts but little action on 
Fehling's solution, but invert-sugar acts powerfully, and some 
processes depend on determining the reducing power before 
and after inversion. Since the polarimetric reading is also 
markedly changed by the inversion, the difference in polariza- 
tion may be employed. Processes of fermentation may be so 
conducted as to remove the sucrose (also any form of glucose) 
while the lactose is unaffected. This method is chiefly valuable 
for recognizing invert- sugar or either of its constituents. 

When inversion methods are used, they must be such as to 
secure prompt inversion of the sucrose without affecting the 
lactose. Experiment shows that citric acid and invertase are 
the most suitable agents. Stokes & Bodmer have worked out 
the citric acid method substantially as follows: 

25 c.c. of the diluted sample are coagulated by addition of i 
per cent, of citric acid, without heating, and made up to 200 c.c. 
plus the volume of the precipitated fat and proteids (see p. 212). 
The liquid portion, which now measures 200 c.c, is passed 
through a dry filter. The reducing power with alkaline copper 
solutions is determined at once upon 50 c.c. of this filtrate. To 



2 28 FOOD ANALYSIS 

another 50 c.c, i per cent of citric acid is added, the solution 
boiled at least 30 minutes/'' and the reducing power also deter- 
mined. The increase over that of the first solution is due to the 
invert-sugar formed by the action of the citric acid on the 
sucrose. It is necessary to bear in mind that the reducing 
equivalents of lactose and invert-sugar are not the same. 
Volumetric method may be employed. 

The following method is based on the difference in polari- 
mctric reading before and after action of invertase. 75 c.c. of the 
diluted milk are placed in a 100 c.c. flask, diluted to about 80 c.c, 
heated to boiling, to correct birotation, cooled, and 10 c.c. of acid 
mercuric nitrate solution added. The mixture is made up to 
100 c.c, well shaken, filtered through a dry filter, and the polari- 
metric reading taken at once. It will be the sum of the efl'ect 
of the two sugars. The volume of the sugar-containing liquid 
is calculated by allowing for the precipitated proteids and fat, 
as described on page 212. 

50 c.c. of the filtrate are placed in a flask marked at 55 c.c, 
a piece of litmus paper dropped in, and the excess of nitric 
acid cautiously neutralized by sodium hydroxid solution. The 
liquid is then faintly acidified by a single drop of acetic acid 
(it must not be alkaline), a few drops of an alcoholic solution of 
thymol are added, and then 2 c.c. of a solution of invertase, 
prepared by grinding half a cake of ordinary compressed yeast 
with 10 c.c. of water and filtering. The flask is corked and 
allowed to remain at a temperature of 35° to 40° for 24 hours. 
The cane-sugar will be inverted, while the milk-sugar will be 
unaffected. The flask is filled to the mark (55 c.c.) with washed 
aluminum hydroxid and water, mixed, filtered, and the polari- 
metric reading taken. The amount of cane-sugar can be de- 
termined from the difference in the two readings by the formula 
on page 120. 

A powerful solution of invertase may be prepared by the 
method recommended by O'Sullivan and Tompson. Brewer's 



CONDENSED MILK 229 

yeast is allowed to stand at a temperature of 15° for a month. 
The liquid is filtered and sufficient alcohol added to give 
about 12 per cent, of absolute alcohol. After a few days the 
liquid is filtered and is ready for use. The alcohol acts as a 
preservative. 

Bigelow and McElroy propose the following routine method 
for the determination of the sugars, including invert- sugars, in 
condensed milk. The solutions --used are: 

Acid Mercuric lodid. — Mercuric chlorid, 1.35 grams; potas- 
sium iodid, 3.32 grams; glacial acetic acid, 2.c.c.; water, 64 c.c. 

Alumina-cream. — See page 118. 

The entire contents of the can are transferred to a porcelain 
dish and thoroughly mixed. A number of portions of about 25 
grams are weighed carefully in loo c.c. flasks. Water is added 
to two of the portions, and the solutions boiled. The flasks are 
then cooled, clarified by means of a small amount of the acid 
mercuric iodid and alumina-cream, made up to mark, filtered, 
and the polarimetric reading noted. Other portions of the milk 
are heated in the water-bath to 55°; one-half of a cake of com- 
pressed yeast is added to each flask and the temperature main- 
tained at 55° for five hours. Acid mercuric iodid and alumina- 
cream are then added, the solution cooled to room temperature, 
made up to mark, mixed, filtered, and polarized. The amount 
of cane-sugar is determined by formula on page 120. Correction 
for the volume of precipitated solids may be made by the double- 
dilution method (p. 21). The total reducing sugar is estimated 
in one of the portions by one of the reducing methods, and if 
the sum of it and the amount of cane-sugar obtained by in- 
version is equal to that obtained by the direct reading of both 
sugars before inversion, no invert-sugar is present. If the 
amount of reducing sugar seems to be too great, the milk-sugar 
must be re-determined as follows: 250 grams of the condensed 
milk are dissolved in water, the solution boiled, cooled to 80°, 
a solution of about 4 grams of glacial phosphoric acid added, 



230 FOOD ANALYSIS 

the mixture kept at 80° for a few minutes, then cooled to room 
temperature, made up to mark, shaken, and filtered. It may 
be assumed that the volume of the precipitate is equal to that 
obtained by mercuric iodid solution. Enough sodium hydroxid 
is then added to not quite neutralize the free acid, and sufficient 
water to make up for the volume of the solids precipitated by 
the phosphoric acid. The mixture is then filtered and the fil- 
trate is measured in portions of 100 c.c. into 200 c.c. flasks. A 
solution containing 20 milligrams of potassium fluorid and half 
a cake of compressed yeast is added to each flask, and the mix- 
ture allowed to stand for 10 days at a temperature between 25° 
and 30°. The invert-sugar and cane-sugar are fermented and re- 
moved by the yeast in the presence of a fluorid, while milk-sugar 
is unaffected. The flasks are filled to the mark and the milk- 
sugar determined either by reducing or by the polariscope. 
The amount of copper solution reduced by the lactose and invert- 
sugar, less the equivalent of lactose remaining after fermenta- 
tion, is due to invert-sugar. 

BUTTER 

Butter is a mixture of fat, water, and curd. The water con- 
tains milk-sugar and the salts of the milk. Common salt is 
usually present, being added after the churning. Artificial 
coloring is frequently used. 

Butter-fat is distinguished from other animal fats in that it 
contains a notable proportion of acid radicles with a small 
number of carbon atoms. Thus, about 91 per cent, consists 
of palmitin and olein and the remainder of butyrin and ca- 
proin, along with small amounts of capr}'lin, caprin, myristin, 
and some others. According to the experiments of Hehner 
& Mitchell, stearin is present only in very small quantity. 
The exact arrangement of the constituents is unknown. 

The composition of commercial butter usually varies within 
the following limits: 



BUTTER 231 

Fat, 78 per cent, to 94 per cent. 

Curd, I " "3 

Water, 5 " "14 

Salt, o " "7 

Butter containing over 40 per cent, of water is sometimes 
sold. Such samples are pale and spongy, lose weight, and 
become rancid rapidly. 

The official methods of the A. O. A. C. for the analysis of 
butter are as follows: 

Preparation of the Sample. — If large quantities of butter 
are to be sampled, a butter trier or sampler may be used. 
The portions thus drawn, about 500 grams, are to be per- 
fectly melted in a closed vessel at as low a temperature as 
possible, and when melted the whole is to be shaken violently 
for some minutes until the mass is homogeneous and suffi- 
ciently solidified to prevent the separation of the water and fat. 
A portion is then poured into the vessel from which it is to be 
weighed for analysis, and should nearly or quite fill it. This 
sample should be kept in a cold place until analyzed. 

Water. — From 1.5 to 2.5 grams are dried to constant weight 
at the temperature of boiling water, in a dish with fiat bottom, 
having a surface of at least 20 sq. cm. The use of clean dry 
sand or asbestos with the butter is admissible, and is necessary 
if a dish with round bottom be employed. 

Fat. — The dry butter from the water determination is dis- 
solved in the dish with absolute ether or with petroleum spirit 
(sp. gr. 0.680). The contents of the dish are then transferred 
to a weighed Gooch crucible with the aid of a wash-bottle filled 
with the solvent, and are washed until free from fat. The cruci- 
ble and contents are heated at the temperature of boiling water 
till the weight is constant. 

The fat may also be determined by drying the butter on 
asbestos or sand, and extracting by anhydrous alcohol-free 
ether. After evaporation of the ether the extract is heated 



232 FOOD ANALYSIS 

to constant weight at the temperature of boihng water and 
weighed. 

Casein, Ash, and Chlorin. — The crucible containing the 
residue from the fat determination is covered and heated, 
gently at first, gradually raising the temperature to just below 
redness. The cover is removed and the heat continued until 
the material is w^hite. The loss in weight represents casein, 
and the residue mineral matter. In this mineral matter dis- 
solved in water slightly acidulated with nitric acid, chlorin 
may be determined gravimetrically with silver nitrate, or, after 
neutralization with calcium carbonate, volumetrically, using 
potassium chromate as indicator. 

Salt. — About 10 grams are weighed in a beaker in por- 
tions of about I gram at a time taken from different parts of 
the sample. Hot w^ater (about 20 c.c.) is now added to the 
beaker, and after the butter has melted, the mass is poured 
into the bulb of a separating funnel, which is then closed and 
shaken for a few moments. After standing until the fat has 
all collected, the water is allowed to run into an Erlenmeyer 
flask, with care not to let fat globules pass. Hot water is again 
added to the beaker, and the extraction is repeated from ten 
to fifteen times, using each time from 10 to 20 c.c. of water. 
The resulting w^ashings contain all but a mere trace of the salt 
originally present in the butter. The chlorin is determined 
volumetrically in the filtrate by means of standard silver nitrate 
and potassium chromate indicator and calculated to sodium 
chlorid. 

Adulteration with Foreign Fats. — The chief adulteration of 
butter consists in the substitution of foreign fats, especially the 
product known as oleomargarin. 

When fats are saponified and the soap treated w^ith acid, the 
individual fatty acids are obtained. It is upon the recognition 
of the peculiar acid radicles existing in butter that the most 
satisfactory method of distinguishing it from other fats is based. 



BUTTER 233 

Since the relative proportion of these radicles differs in dif- 
ferent samples, the quantitative estimation cannot be made 
with accuracy; but when the foreign fats are substituted to 
the extent of 20 per cent, or more, the adulteration can be 
detected with certainty and an approximate quantitative deter- 
mination made. 

The detection of adulteration of butter-fat by other fats is 
generally carried out by the determination of the volatile acid, 
but some other confirmatory processes are occasionally em- 
ployed. The data for interpreting results will be found in the 
table on page 165. 

Volatile Acids. — The glycerol-soda method (page 143) is 
sufficient for the purpose. No advantage w^ill result from 
using the tedious method with alcoholic solution; indeed, 
under ordinary circumstances the latter is probably less accu- 
rate. 

Butter (5 grams) yields a distillate requiring from 24 to 34 
c.c. of decinormal alkali. Several instances have been pub- 
lished in which genuine butter has given a figure as low as 
22.5 c.c, but such results are uncommon. The materials 
employed in the preparation of oleomargarin yield a distillate 
requiring less than i c.c. of alkali. Commercial oleomargarin 
is usually churned with milk in order to secure a butter flavor, 
and, thus acquiring a small amount of butter-fat, yields dis- 
tillates capable of neutralizing from i to 2 c.c. of alkali. 

If coconut oil (see page 165) has been used in the prepara- 
tion of the oleomargarin, the figure will be higher, but there 
will still be no difficulty in distinguishing pure butter. 

Saponification Value. — In the absence of coconut oil, the 
saponification value will give valuable indications as to the 
purity of a butter sample. It is possible to make oleomar- 
garin, by the addition of coconut oil, which would have the 
same saponification value as pure butter. 

Specific Gravity. — According to Skalweit, the greatest dif- 
21 



234 FOOD ANALYSIS 

crcnccs Ix'twccn ihc specific j^ravily of buUcr and its adullcr- 
anls arc found at a temperature of 35°, l)ut tlic determina- 
tion is more conveniently made at the temperature of boiling 
water. The Sprengel tube or Westphal balance may be em- 
ployed for the purpose. 

The determination of the Reichert number will usually give 
sufficient information as to the nature of a butter sample. In 
doubtful cases it may be of advantage to apply other tests as 
corroborative evidence. The determination of soluble and 
insoluble acids may be employed, but Valenta's test and the 
refractometric examination are especially mentioned as fur- 
nishing results with little trouble in a short time. 

Soluble and Insoluble Acids. — The proportion of insoluble 
acids in butter is usually about 87.5 per cent, and of soluble 
acids, calculated as butyric, about 5 per cent. The insoluble 
acids may be present to the extent of 88.5 per cent., but, ac- 
cording to most authorities, they will only reach 90 per cent, 
in the presence of adulterants. These figures apply to fresh 
samples. After keeping until rancidity has developed the 
proportion of insoluble acids may be increased i per cent, or 
more. 

Mixtures of butter, oleomargarin, and coconut oil may have 
the same proportion of insoluble acids as butter-fat. 

Valenta^s Test. — Jones recommends the employment of a 
standard butter-fat with which to standardize each fresh 
batch of acid, and dilution of the acid to such a point that the 
turbidity temperature with this fat is 60°. In this way the 
results are comparable with those of previous tests. 

With such acid, oleomargarin gave temperatures from 95° 
to 106°, and generally from 100° to 102°. 

Milk test. — The following test was proposed by Waterhouse " : 
50 c.c. of fresh whole milk are placed in a 100 c.c. beaker, heated 
nearly to boihng and a lump of the sample (5 to 10 grams) 
stirred in, preferably with a wooden rod, until the fat is melted. 



BUTTER 235 

The beaker is placed in cold water and the stirring continued 
until the temperature falls to the solidifying point of the fat. 
Butter fat will be granular and not easily collected into a lump, 
but oleomargarin will collect readily. 

Rejractometric Examination. — This is most satisfactorily 
made by the oleorefractometer or the butyrorefractometer. 
Jean prepares the sample for examination in the former as 
follows: 30 grams of butter are melted in a porcelain dish at 
a temperature not exceeding 50°, stirred well with a pinch or 
two of gypsum, and allowed to settle out at the same temper- 
ature. The supernatant fat is decanted through a hot-water 
funnel plugged with cotton and poured while warm into the 
prism of the apparatus, stirred with the thermometer until the 
fat has cooled to 45°, and the deviation observed. Ether must 
not be used for the solvent, as minute traces of it seriously 
influence the result. 

The following table is a summary of the results obtained by 
several observers, including Jean and Pearmain. The oleo- 
refractomer was different from those shown on page 154, but 
the figures have a relative value : 

Degrees in 
Oleorefractometer . 

Butter, — 25 to — 34, usually — 30 

Oleomargarin, — 13 to — 18 

Butter with 10 p. c. oleomargarin ( — 17), —28 

Butter with 50 p. c. oleomargarin, — 23 

Lard, — 8 to — 14 

Coconut oil, • — 59 

Arachis oil, 3-5 to 7 

Cottonseed oil, 12 to 23 

Cottonseed "stearin," 25 

De Bruyn found as low as — 21 in butter from animals fed 
on linseed cakes. A mixture of coconut oil and oleomargarin 
may be made having the same refractive power as pure butter. 
Evidently, therefore, it is not possible from this datum alone 
to state that a given sample is pure butter, but a sample ex- 



236 FOOD ANALYSIS 

hibiling a refraction of — 20° or under may be pronounced 
adulterated. 

Zeiss' butyrorefractometer is now much used, the resuUs 
being of service in sorting samples and as confirmation. 

Commercial forms of oleomargarin and butter exhibit char- 
acteristic differences on heating, which may be utilized for 
rapidly sorting a collection of samples. When butter is heated 
in a small tin dish directly over a gas flame, it melts quietly, 
foams, and may run over the dish. Oleomargarin, under 
the same conditions, sputters noisily as soon as heated and 
foams but little. Even mixtures of butter and other fats show 
this sputtering action to a considerable extent. The effect 
depends upon the condition in which the admixed water exists, 
and the test is not applicable to butter which has been melted 
and reworked (renovated or process butter). 

An alcoholic solution of sodium hydroxid, heated for a 
moment with butter, and then emptied into cold water, gives 
a distinct odor of pineapples, while oleomargarin gives only 
the alcoholic odor. 

Renovated Butter. — So-called "process" or "renovated" 
butter, made by rendering old or inferior samples, purifying 
the fat, coloring, salting, and molding it, is now a familiar com- 
mercial article. Process butter when heated in a dish sputters 
with but little foaming, as does oleomargarin; but yields with 
alcoholic soda the pineapple odor, as does butter. The fat of 
process butter gives refractometric data and Reichert-Meissl 
number similar to those of ordinary dairy butter, but is said 
to give a different figure with Valenta's test. If, therefore, 
a sample sputters in the pan, but gives the other reactions for 
butter, as just noted, it may be assumed to be process butter. 
Hess & Doolittle state that the curd of process butter has 
characteristic qualities, and propose the following method for 
detecting it: 

50 grams of the sample are melted in a beaker at about 



BUTTER 237 

50°. Ordinary butter yields a clear fat almost as soon as 
melted, while with process butter the fat may remain turbid 
for a long while. When the curd has largely settled, as much 
of the fat is poured off as possible, and the remaining mix- 
ture is thrown on a wet filter, by which the water will drain 
away, carrying the soluble proteids and salt. A few drops of 
acetic acid are added to the filtrate and the mixture is boiled. 
The filtrate from ordinary butter gives a slight milkiness, but 
that from process butter gives a flocculent precipitate. Quan- 
titative examination is made by dissolving 50 grams of the 
sample in ether; if it is ordinary butter, the curd is so finely 
divided that it remains suspended for some time. As much 
as possible of the solution is decanted and the mass transferred 
to a separator, the casein, water, and salt removed, and the re- 
mainder washed three times, at least, with ether to remove the 
fat. The curd is collected on a filter, washed with water, and 
the nitrogen determined by treating the precipitate with the 
filter by the Kjeldahl- Gunning method. The filtrate from the 
curd is made slightly acid with acetic acid, boiled, the pre- 
cipitated proteids collected on a filter, and the total nitrogen 
determined. The factor 6.38 may be used in each case for 
converting the nitrogen into proteids. 

A distinction between ordinary and process butter may 
often be made by microscopic examination under polarized 
light with crossed nicols {i. e., dark field), when the process 
butter appears mottled, owing to the presence of crystals. 

Butter Colors. — Butter and butter substitutes are usually 
artificially colored. Preparations of turmeric and annatto or 
azo-colors allied to methyl-orange are used. The latter forms 
may be detected by the test devised by Geisler. A small amount 
of the sample, or, better, the fat filtered from it, is mixed 
on a porcelain plate with a little fuller's earth. Azo-colors 
give promptly a red mass, while if they are not present, the mix- 
ture becomes only yellow or light brown. All samples of 



238 FOOD ANALYSIS 

fuller's earth are not equally active, and tests should be made 
with ditlerent samples by using fat known to contain the azo- 
compound until a good specimen of the earth is secured. 

For the detection of very minute quantities of the color, the 
sample may be dissolved in light petroleum, and the fuller's 
earth added to the solution, when the pink color will appear 
as a distinct ring or zone at the edge of the deposited layer of 
the reagent. 

Low has proposed the following test for the yellow azo-color: 
A few cubic centimeters of the filtered fat are mixed in a large 
test-tube with an equal volume of a mixture of one part strong 
sulfuric acid and four parts glacial acetic acid. The contents 
of the tube are then heated almost to boiling and thoroughly 
mixed by violently agitating the bottom of the tube. When now 
allowed to stand and separate, the lower layer of mixed acids 
will be strongly colored wine-red if the azo-color be present. 
Pure butter-fat imparts no color to the acids, or, at most, only 
a faint brownish tinge. 

For turmeric and annatto mixtures, Martin's test will 
usually be satisfactory: 2 c.c. carbon disulfid are mixed with 
15 c.c. of alcohol, by adding small portions of the disulfid 
to the alcohol and shaking gently; 5 grams of the butter- 
fat are added to this mixture in a test-tube and shaken. The 
disulfid falls to the bottom of the tube, carrying with it the 
fatty matter, while any artificial coloring-matter remains in 
the alcohol. The separation takes place in from one to three 
minutes. If the amount of the coloring-matter is small, more 
of the fat may be used. If the alcoholic solution be evaporated 
to dryness and the residue treated with concentrated sulfuric 
acid, annatto will be indicated by the production of a greenish- 
blue color. With many samples of oleomargarin, a pink tint 
wdll be produced, which indicates an azo-color. 

Palm oil is sometimes used as a coloring agent in butter- 
substitutes. Crampton & Simons'*^ have found that two tests 



BUTTER 239 

devised for detection of rosin-oil can be satisfactorily adapted 
to detection of palm oil. Success depends on several points. 
The sample must be kept in a cool dark place until used, filtered 
at a temperature not above 70°, the heating as brief as possible, 
and promptly tested. The reagents must be pure and colorless. 

Halphen method. 100 c.c. of the filtered fat are dissolved in 
300 c.c. petroleum spirit and shaken out with 50 c.c. of potas- 
sium hydroxid solution (0.5 per cent of hydroxid). The water 
is drawn off, made distinctly acid with hydrochloric acid, and 
shaken out with 10 c.c. of carbon tetrachlorid. This solution 
is drawn off, and part of it tested by adding to it 2 c.c. of a mix- 
ture of I part crystallized phenol in 2 parts carbon tetrachlorid. 
To this add 5 drops of hydrobromic acid (sp. gr. 1.19). The 
test is best performed in a porcelain basin and the contents 
mixed by agitating gently. Palm oil gives almost immediately 
a bluish-green liquid. 

Liebermann-S torch method. 10 c.c. of the filtered fat are 
shaken with an equal volume of acetic anhydrid, one drop of 
sulfuric acid (sp. gr. 1.53) is added and the mixture shaken 
for a few seconds. If palm oil be present, the heavier layer 
separating will be blue with a tint of green. 

For detection of yolk of egg, which has been proposed as a 
color for oleomargarin, see under '' Egg Substitutes." 

Preservatives. — -The preservatives used in milk may be found 
in limited amount in butter, but a mixture of boric acid and 
borax is often added as a substitute for salt. It will be detected 
by the method given on page 82 in the water obtained by melt- 
ing the butter and allowing the mass to settle. 

Glucose is sometimes used as a preservative, especially in 
butter intended for export to tropical countries. Crampton 
found as much as 10 per cent, in a sample of highly colored 
butter intended for exportation to Guadeloupe. For the de- 
tection of glucose the phenylhydrazin test might be used. For 
determination Crampton used the following method : 10 



240 FOOD ANALYSIS 

grams of the sample were washed with successive portions of 
convenient bulk, the solution made up to 250 c.c, and an aliquot 
portion determined, as given on page 113. The solution may 
also be clarified by alumina-cream or acid mercuric nitrate and 
examined in the polarimeter. 

Geisler found paraflfin in oleomargarin; his observation has 
been confirmed by several other chemists. Geisler uses the 
specific gravity of the rendered fat as a sorting test, making 
special examination only of samples that show below 0.9018 

_ _ 00 

at Jy^o. Microscopic examination under polarized light, with 
and without selenite, will often show amorphous masses of 
paraffin mixed with the crystals of fat. To isolate the paraffin, 
Geisler saponifies 2.5 grams of the fat with 20 c.c. of alcohol 
and I gram of potassium hydroxid, and dilutes the liquid with 
an equal bulk of water. By alternately heating and cooling 
the liquid much of the unsaponifiable matter may be collected. 
It is also possible to isolate it by the process given on page 159, 
or by destroying the fat by strong sulfuric acid. It must be 
borne in mind that most fats contain notable amounts of un- 
saponifiable matter, and hence the material must be identified as 
parafiin. 

CHEESE 

Cheese is the curd of milk which has been separated from 
it, pressed, and undergone some fermentation. The precipita- 
tion is produced either by allowing the milk to become sour 
— when the lactic acid is the agent — or by rennet. The first- 
named method is mainly applied to the manufacture of so- 
called Dutch or sour-milk cheese, green Swiss cheese, and 
cottage cheese. More commonly cheese is obtained by means 
of rennet derived from the fourth stomach of the calf. The 
action is due to an enzym which acts directly on the proteids 
and does not produce its efifect through the inter\'ention of 
acids. The curd (cheese) undergoes, by keeping, various 



CHEESE 241 

decompositionSj some essentially putrefactive, and due to the 
action of microbes. The decomposition of the cheese is termed 
"ripening." 

In the sour milk cheeses, ripening is restricted intention- 
ally, since there is liability to an irregular and miscellaneous 
bacterial growth by which the fermentations may be carried 
too far, undesirable and even harmful products being formed. 
Such cheeses are intended for prompt use. 

Cheese contains no casein, if by this term is meant the proteid 
as it exists in milk, or when precipitated from milk by acids. 
When milk is coagulated by rennet, only a part of the proteids 
enter into the curd; true casein contains about 15.7 per cent. 
of nitrogen, but the proteid matter of cheese contains about 
14.3 per cent. Under the process of ripening this is further 
decomposed, amido- and ammonium compounds, peptones 
and albumoses, being formed. 

The following figures, obtained by Van Slyke, will serve 
to give some idea of the extent to which the curd is changed 
in ripening. The figures represent average percentage on the 
total nitrogen. The cheese was an American cheddar: 





Green Cheese; 


After Five Months 


Soluble nitrogen compounds, . . . 


4-23 


35-52 


" amido 


none 


11.66 


" ammonium " 


none 


2.92 



Van Slyke' s experiments seem also to indicate that the cheese 
ripened more rapidly when the curd was precipitated by a 
larger quantity of rennet and, especially, that cheese rich in 
fat ripened more rapidly than skim-milk cheese. 

In addition to the fat and nitrogenous compounds just men- 
tioned, cheese may contain a small amount of milk-sugar and 
of lactic and other organic acids. There is present also a cer- 
tain proportion of mineral matter, alkaline and earthy phos- 
phates, along with any salt that has been added. Traces of 

nitrates have been found. 
22 



242 FOOD ANALYSIS 

Skimmed milk is not infrequently used for the production 
of cheese. Partially-skimmed milk is used in the preparation 
of certain Dutch cheeses. Foreign fats, such as are used in 
the manufacture of oleomargarin, are sometimes incorporated, 
the article being known as "filled cheese." 

The ash of cheese consists largely of calcium i)hosphate and 
salt. Mariani & Tasselli have estimated the total ash, 
chlorin, calcium, and phosphoric acid in 15 samples of 
cheese. The amounts of salts (calculated from the chlorin) de- 
pend on the mode of salting. The proportion of phosphoric 
oxid was always greater than that necessary to form trical- 
cium phosphate, ranging from 1.07 and 1.08 equivalents of 
phosphoric anhydrid to calcium oxid in cheese made from 
sour milk to 1.56 to i in Gorgonzola, 1.67 to i in skim-milk 
cheese, and 1.75 to i in Edam cheese. The largest quanti- 
ties of calcium and phosphoric oxid were found in sheep's- 
milk cheese and in cheese made from sour milk, whence it 
follows that acidity does not prevent the precipitation of cal- 
cium phosphate in the curds. The excess of phosphoric oxid 
obtained was attributed to acid phosphates. 

The salt in cheese usually ranges between i and 4 per cent. 

Analytic Methods. — The analytic points usually deter- 
mined in regard to cheese are water, fat, casein, ash, the pres- 
ence of fats other than butter-fat, and coloring-matters. 

In addition to this, especially in comparing the qualities of 
genuine cheeses, the proportion of proteic, amidic, and ammo- 
niacal nitrogen is of value. 

Care should be taken to select for analysis a sample which 
represents the average composition of the entire cheese. 

The following methods for the determination of water, fat, 
ash, total nitrogen, and acidity have been adopted by the A. O. 
A. C: 

Sampling. — When the cheese can be cut, a narrow wedge- 
shaped segment, reaching from the outer edge to the center 



CHEESE 243 

of the cheese, is taken. This is to be cut into strips and passed 
through a sausage-grinding machine three times. When the 
cheese cannot be cut, samples are taken by a cheese trier. If 
only one plug can be obtained, this should be perpendicular 
to the surface, at a point one-third of the distance from the edge 
to the center of the cheese. The plug should reach entirely 
through, or only half-way through, the cheese. When possible, 
draw three plugs — one from the center, one from a point near 
the outer edge, and one from a point half-way between the 
other two. For inspection purposes, the rind may be rejected; 
but for investigations requiring the absolute amount of fat in 
the cheese, the rind is included in the sample. It is preferable 
to grind the plugs in a sausage machine, but when this is not 
done, they should be cut very fine and carefully mixed. 

Water. — Between 2 and 5 grams of the sample should be 
placed in a weighed platinum or porcelain dish which con- 
tains a small amount of material, such as freshly ignited asbestos 
or sand, to absorb the fat that may run out. This is then heated 
in a water-oven for 10 hours and weighed; the loss in weight 
is considered as water. If preferred, the dish may be placed 
in a desiccator over concentrated sulfuric acid and dried to con- 
stant weight, but this may require many days. The acid 
should be renewed when the cheese has become nearly dry. 

Fat. — The extraction-tube described on page 200 is prepared 
as follows: Cover the perforations in the bottom of the tube 
with asbestos, and on this place a mixture containing equal 
parts of anhydrous copper sulfate and pure dry sand to the 
depth of about 5 cm., packing loosely, and cover the upper 
surface with a film of asbestos. On this are placed from 2 to 5 
grams of the sample, the mass extracted for 5 hours with anhy- 
drous ether, then removed and ground to fine powder with pure 
sand in a mortar. The mixture is placed in the extraction 
tube, the mortar washed free from all matters with ether, the 
washings being added to the tube, and the extraction is con- 



244 FOOD ANALYSIS 

tinued for lo hours. The fat so obtained is dried at ioo° to 
constant weight. 

Here, as in most extractions, carbon tetrachlorid can be 
substituted for ether, but the results obtained are not neces- 
sarily equivalent. 

Total Nitrogen. — This is determined by the Kjeldahl-Gun- 
ning method, using 2 grams of the sample. The percentage^ 
multiplied by 6.38, gives the nitrogen compounds. 

Ash. — The dry residue from the water determination may 
be taken for the ash. If the cheese be rich, the asbestos will 
be saturated therewith. This mass may be ignited carefully, 
and the fat allowed to burn off, the asbestos acting as a wick. 
No extra heating should be applied during the operation, as 
there is danger of spurting. When the flame has died out, 
the burning may be completed in a muffle at low redness. 
When desired, the salt may be determined in the ash by titra- 
tion with silver nitrate and potassium chromate. 

Provisional Method for the Determination oj the Acidity in 
Cheese. — Water at a temperature of 40° is added to 10 grams 
of finely divided cheese until the volume equals 105 c.c, agitated 
vigorously, and filtered. Portions of 25 c.c. of the filtrate 
corresponding to 2.5 grams of the cheese are titrated with deci- 
normal solution of sodium hydroxid, using phenol-phthalein 
as indicator. The amount of acid is expressed as lactic acid. 

The above processes may be advantageously modified in 
some respects. The determination of water may be made by 
the extraction of the cheese with alcohol and ether and drying 
of the alcohol-ether extract and fat-free solids separately. 
Blyth recommends this method as more accurate and less 
tedious than the direct drying. In the determination of ash 
it will be better to extract the charred mass with water and 
proceed as described in the determination of the ash of milk. 

The fat extracted by ether may be examined for other than 
butter-fat by the distillation method in the usual way. When 



CHEESE 245 

the composition of the fat is alone desired, it may often be ex- 
tracted by simple methods. Pearmain & Moor recommend 
that 50 grams be chopped fine and tied up in a muslin bag, 
which is placed in a water-bath. When the water is heated, the 
fat will generally run out clear. If not clear, it can be filtered 
through paper. 

Henzold suggests the following : 300 grams of the powdered 
cheese are agitated in a wide-neck flask with 700 c.c. of 5 per 
cent, solution of potassium hydroxid previously warmed to 20°. 
In about 10 minutes the cheese dissolves, the fat floats, and by 
cautious shaking may be collected in lumps. The liquid is 
diluted, the fat removed, washed in very cold water, kneaded 
as dry as possible, melted, and filtered. It is claimed that the 
fat is not altered in composition by the process. 

The fat of cheese may be estimated by the centrifugal method, 
as follows: 

About 3 grams of the mixed cheese in small fragments are 
weighed and transferred to the bottle, the last portions being 
washed in with the acid of water. A few drops of ammonium 
hydroxid are added, and sufficient water to make the liquid 
about 15 c.c. The liquid is warmed with occasional shaking 
until the cheese is well disintegrated, and then treated as a 
sample of milk. The percentage of fat is found by multiply- 
ing the percentage reading by 15.45 and dividing by the num- 
ber of grams of cheese taken for analysis. 

Chattaway, Pearmain, & Moor use the following modifica- 
tion: 2 grams of the cheese are placed in a small dish and 
heated on the water-bath with 30 c.c. of concentrated hydro- 
chloric acid until a dark, purplish-colored solution is produced. 
The mixture is now poured into the test bottle, portions of 
solution remaining in the dish rinsed with the hydrochloric acid 
fusel-oil mixture into the bottle, and, finally, enough strong hot 
acid added to fill the bottle up to the mark. It is then whirled 
for about a minute. The difficulty in this method is to get all 



246 FOOD ANALYSIS 

the fat into the bottle. It is best to weigh the cheese in the 
bottle. 

Bondzynksi applies the Werner-Schmid method to the de- 
termination of fat in cheese, as follows: A weighed quantity 
of the linely-shredded cheese is placed in the tube and decom- 
posed with 20 c.c. hydrochloric acid of specific gravity i.i, 
containing about 19 per cent, true acid. On cautiously warm- 
ing over wire gauze, the melted fat rises to the surface. After 
cooling, 30 c.c. of ether are added and the tube warmed very 
gently until the acid and ethereal solution of fat separate sharply. 
Centrifugal force helps this, but is not essential. After the vol- 
ume of ether has been read off, 20 c.c. are pipetted off into a 
weighed Erlenmeyer f]ask. From this, the quantity of fat in 
the entire solution may be calculated. 

Lactose. — This may be estimated by boiling the finely di- 
vided cheese wdth water, filtering, and determining the reduc- 
ing power of the filtrate on Fehling's solution. 

Determination of Proteid Nitrogen (Stutzer's Method). — 0.7 
to 0.8 gram of the cheese are placed in a beaker, heated to 
boiling, 2 or 3 c.c. of saturated alum solution added to decom- 
pose alkaline phosphate, then copper hydroxid mixture (see 
page 37) containing about 0.5 gram of the hydroxid, and stirred 
in thoroughly; when cold, the mass is filtered, washed with 
cold water, and, without removing the precipitate from the filter, 
the nitrogen determined by the Kjeldahl-Gunning method. 
Before distillation, sufficient potassium sulfid solution must be 
added to precipitate the copper. 

Ammonium Compounds. — About 5 grams of cheese are 
rubbed up in a mortar with water, transferred to a filter, and 
washed with a liter of cold water. The filtrate is concentrated 
by boiling (if alkaline, it must be neutralized before heating), 
barium carbonate added, the liquid distilled, and the ammo- 
nium hydroxid in the distillate estimated by titration with stan- 
dard acid. 



CHEESE 247 

According to Stutzer, magnesia or magnesium carbonate 
(the latter usually contains some magnesia) should not be used 
to free the ammonia, as some of the amido-compounds may 
be decomposed. 

Amido-compounds.— The nitrogen as amido-compounds is 
estimated by subtracting from the figure for total nitrogen the 
sum of the proteid and ammoniacal nitrogen. If nitrates are 
present, the nitrogen as such should also be determined and 
substracted. 

Van Ketel & Antusch propose the following methods for 
estimating the nitrogen compounds: 

Ammonium Compounds. — The sample, powdered with the 
addition of sand, is distilled wtth water and barium carbonate, 
and the distillate received in a measured quantity of standard 
sulfuric acid, and, after boiling, the excess of acid is neutral- 
ized with standard sodium hydroxid, using rosolic acid as 
indicator. 

Amido-compounds. — These are estimated by macerating the 
powdered cheese in water for 15 hours at the ordinary tem- 
perature. After adding a little dilute sulfuric acid (i : 4), the 
proteids and peptones are precipitated by phosphotungstic 
acid. The precipitate is filtered off and washed with water 
containing a little sulfuric acid. The filtrate is made up to a 
definite bulk, and the nitrogen is determined in an aliquot por- 
tion of the liquid by the Kjeldahl- Gunning process, allow- 
ance being made for the nitrogen existing as ammonium. 

Peptones and Alhumoses. — These are determined jointly by 
boiling the powdered cheese (mixed with sand as before) with 
water and filtering from the undissolved casein and albumin. 
In an aliquot portion of the filtrate the peptones and albu- 
moses are precipitated by adding dilute sulfuric acid and 
phosphotungstic acid. After washing with acidulated water 
the nitrogen in the precipitate is determined by the Kjeldahl- 
Gunning process. 



248 FOOD ANALYSIS 

The total nitrogen of the cheese is also determined, and after 
allowing for the nitrogen existing as other forms, the balance 
is calculated to casein. 

Poisonous Metals. — Lead chromate has been found in the 
rind of cheese, and finely divided lead in a number of Cana- 
dian cheeses. In England zinc sulfate has been employed 
under the name of cheese spice to prevent the heading and crack- 
ing. Arsenic has also been found; it may be detected by 
Reinsch's test. Lead, zinc, and chromium may be detected 
by ashing a portion of the sample in a porcelain crucible and 
proceeding as on page 58. 

ANALYSES OF VARIOUS CHEESES 

(Reports by W. A. Chattaway, T. M. Pearraain, and C. G. Moor) 

Reichert-Meissl 
Name. Water. Ash Fat. Number. N. 

Cheddar, 33.0 4.3 29.5 24.2 4.31 

Gorgonzola, 40.3 5.3 26.1 22.1 4.36 

Dutch, 41.8 6.3 10.6 27.0 5. II 

Gruyere, 28.2 4.7 28.6 30.0 4.93 

Stilton, 19.4 2.6 42.2 29.0 4.73 

Cheshire, 37.8 4.2 31.3 31.6 4.03 

Gloucester, 33.1 5.0 23.5 31.4 4.99 

Camembert, 47.9 4.7 41.9 31.0 3.83 

Parmesan, 32.5 6.2 17. i 28.0 6.86 

Roquefort, 29.6 6.7 30.3 36.8 4.45 

Double Cream, 57.6 3.4 39.3 31.2 3.14 

Filled (United States), 30.6 3.6 27.7 3.0 4.84 

The common American cheese is known as Cheddar. Ac- 
cording to Van Slyke, this has, when ripe, about the following 
average composition : 

Water, 3i-5o per cent. 

Fat, 37.00 

Proteids, 26.25 " 

Ash, sugar, etc., 5.25 " 

FERMENTED MILK PRODUCTS 

The usual fermentation of milk is the conversion of the 
lactose into lactic acid, but by special methods other changes 



FERMENTED MILL PRODUCTS 249 

may be substituted. These modified fermentations are of 
rather ancient origin, and being produced by mixture of organ- 
isms, the products are complex and irregular. The proteids 
are more or less changed into proteoses and peptones. 

Kumiss is milk which has undergone alcoholic fermentation. 
The inhabitants of the steppes of Russia prepare it from mares' 
milk. When cows' milk is used, cane-sugar must be added. 
It is often made by adding cane-sugar and yeast to skim-milk. 

P. Vieth gives the following analysis of kumiss at successive 
stages of fermentation: 

KUMISS FROM COWS' MILK 

One One Three 

One Day. Week. Month. Months. 

Alcohol, I.I 0.9 i.o I.I 

Solids, II. 3 8.9 8.6 8.5 

Fat, 1.6 1.4 1.5 1.5 

Casein, 2.0 2.0 1.9 1.7 

Albumin, .... 0.3 0.2 0.2 o.i 

Sugar, 6.1 3.1 2.2 1.7 

Lactic acid, 0.2 0.9 1.3 1.9 

Lactoproteid and peptone, ... . 0.3 0.5 0.7 0.9 

Soluble ash. o.i 0.2 0.2 0.2 

Insoluble ash, 0.4 0.3 0.3 0.3 

The item "lactoproteid and peptone" refers to the sub- 
stances precipitated by tannin after removal of the casein and 
albumin. 

KUMISS FROM MARES' MILK 

At the Nitrogenous Lactic 

End of: Alcohol. Fat. Matters. Acid. Sugar. Ash. 

I day, 2.47 1.08 2.25 0.64 2.21 0.36 

8 days, 2.70 1.13 2.00 1.16 0.69 0.37 

22 " .2.84 1.27 1.97 1.26 0.51 0.36 

Kefyr. — This is usually made from cows' milk. It has been 
used in the Caucasus for centuries. For its preparation a pecu- 
liar ferment is used, which is contained in the kefyr grains. 
These are first soaked in water, by which they arc caused to 
swell and are rendered more active, and then added to llie milk. 



250 FOOD ANALYSIS 

If taken out oi the milk and dried, the grains may be used 
repeatedly. 

The following are analyses of kefyr: 

KoNic. Hahmarsten. 

Alcohol, 0.7 s 0.72 

Fat, .1.44 3.08 

Casein, 2 .88 2.94 

Albumin, 0.36 0.18 

Hemialbumose, 0.26 0.07 

Peptone 0.04 

Sugar, 2.41 2.68 

Lactic Acid, 1.02 0.73 

Ash, 0.68 0.71 

According to Konig, good kefyr will not contain more than 
I per cent, of lactic acid. 

Analytic Methods. — Fixed solids and ash are determined 
by evaporations of a weighed amount in a platinum basin as 
described on page 200. Acidity is determined by filtration with 
-^- alkali, using phenolphthalein or methyl-orange as an indica- 
tor. The amount of acidity is expressed in terms of lactic acid. 
The Kjeldahl- Gunning method will give the total nitrogen. 
For further examination of the nitrogenous bodies, the methods 
given on pages 246 and 247 may be applied. Total reducing 
sugars may be estimated as given on page 113. If sucrose 
and common yeast have been added, the fermented material 
will be likely to contain invert-sugar, with unchanged lactose 
and sucrose, and the method of examination of sweetened con- 
densed milk may be applicable. Fat can, probably in all cases, 
be determined with sufficient accuracy by the L-B. process. 
If it be desired to make polarimetric readings, the liquid should 
be clarified with acid mercuric nitrate solution (page 211), as 
some partly hydrolyzed proteids which have rotatory power 
may not be precipitated by other reagents. The determination 
of alcohol accurately is difficult, as the quantity is usually small. 
The cautious distillation of a considerable volume of the ma- 



FERMENTED MILK PRODUCTS 25 1 

terial previously neutralized with a little sodium hydroxid will 
yield a distillate in which alcohol may be determined by specific 
gravity. 

Preservatives are not likely to be used, since they would 
interfere with the fermentation, but attempts may be made to 
secure better keeping by adding some preservative after the 
fermentation has occurred. In some cases, therefore, tests 
for boric acid, formaldehyde, and salicylic acid should be made, 
as these will be most likely to be used. 



252 FOOD ANALYSIS 

NON-ALCOHOLIC BEVERAGES 

TEA 

Tea is the prepared leaf of several species of Thea. Black 
and green tea are derived from the same plant, the difference 
being due to the preparation. The quality of tea depends much 
upon the age of the leaf and the time of picking. Figure 
46 shows the tea leaf (i) and the mate (Paraguay tea) leaf (2). 

Many pickings are made in a 
season, the first lacing of the 
finest quality. 

Black tea is prepared by ex- 
posing the leaves to the sun until 
they have withered. They are 
then rolled and again set aside, 
usually in the sun, covered with 
a white 'cloth until fermentation 
takes place. They are then ex- 
posed in a thin layer until they 
have become quite dark, and arc 
finally dried by heat. 
Pig. 46. Green tea undergoes no fer- 

mentation. In Japan, the leaves 
are steamed until soft, rolled, and dried; in China, they are 
heated in pans. 

In addition to tannin and the usual plant constituents, tea, 
contains a notable proportion of caffein. In a given variety 
of tea, the proportion of caffein usually, but not always, bears 
some relation to the quality, and so does the soluble ash and 
water-extract. 

Cajjein (thein), trimethylxanthin, has been found in tea, 
coffee, mate (Paraguay tea), gauarana, and kola. When slowly 
crystallized from its solution in chloroform or water, it forms 




TEA 253 

light, silky flexible needles. The proportion of water found 
by experiment is rather less than one molecule, owing probably 
to loss by efflorescence. It becomes anhydrous at 100°, and if 
the heating be long continued, a little is volatilized, but it does 
not volatilize with steam. It melts at 231 to 230°, and at 384° 
boils with partial decomposition. It is slightly soluble in cold 
water, but dissolves readily in hot, giving a bitter solution. 
It is slightly soluble in alcohol, less so in absolute alcohol, 
only sparingly in cold ether, nearly insoluble in petroleum 
spirit and freely in chloroform and benzene. It is decom- 
posed by heating with dilute solution of sodium hydroxid, 
barium hydroxid, or calcium hydroxid. 

Caffein responds to the so-called "murexid" test. A 
small amount is dissolved in a few drops of hydrochloric acid, 
a little potassium chlorate added, the liquid evaporated to dry- 
ness on the water-bath, and the residue exposed to the vapor of 
ammonium hydroxid; a deep purple will be produced. 

The following analyses by Kozai indicate the difference in 
composition between green and black Japan teas. The figures 
represent p^centage on the dry material : 

Original Leaves. Green Tea. Black Tea. 

Crude fiber, 10.44 10.06 10.07 

" protein, 37.33 37.43 38.90 

Ether extract, 6.49 5.52 5.82 

Other nitrogen-free extract, ... .27.86 3i-43 35-39 

Ash, 4.97 4.92 4.93 

CaflFein, 3.30 3.20 3.30 

Tannin, 12.91 10.64 4-89 

Water-extract, 5o-97 53-74 47-23 

Nitrogen, total, 5.97 5.90 6.22 

" of albuminoid, 4. 11 3.94 4. 11 

" of caffein, . . 0.96 0.93 0.96 

" of amido-compounds,. 0.91 1.13 1.16 

Indian teas. Results from a great number of examinations: 

Moisture, 5.83 to 6.32 per cent. 

Insoluble leai, 47-i2 " 55-87 " 

Extract, 37-8o " 40-35 " 

Tannin, 13.04 " 1S.87 " 

Caffein, 1.88 " 3.24 

Ash, total, 5.05 " 6.02 " 

" soluble in water, 3.12 " 4.28 " 

" insoluble in acid, 0.12 " 0.30 " 



254 



FOOD ANALYSIS 



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TEA 



255 



It is probable that the proportion of caffein in the above 
analyses is slightly underestimated as the determination was 
made by treating the watery extract with magnesia, evapo- 
rating to dryness, and extracting with ether. 

The tea leaf is ovate-lanceolate with short stem not sharply 
distinguished from the blade. The distal two-thirds of the 
leaf is marked by serrations with slightly curved spines. At the 
insertion of these spines the leaf tissue is thickened. This 
structure is wanting in young leaf buds. The venation is a 




Fig. 47. — Epidermis of Under Surface of Tea-leaf, 
sp, stoma; h, hair; m, cells containing chlorophyl. (X 160.) 



midrib running to the extreme end of the leaf with frequent 
lateral nearly opposite branchings anastomosing near the edge 
and sending off secondary branches to the extreme edge. The 
apex of the tea leaf is often distinctly notched, whereas most 
other leaves are pointed. The stomata and hairs are fairly 
characteristic. Figure 47 is from Moeller's work."**^ 

Adulteration. — The substitution of inferior grades of tea 
for those of fmer aroma and strength is the common adulter- 
ation of tea. Other forms are: additions, such as sand, ex- 



256 FOOD ANALYSIS 

hausted leaves, foreign leaves, and materials to increase astrin- 
gency, especially catechu. Green tea is often colored or ''faced" 
with Prussian blue, indigo, or turmeric, and black tea with 
graphite. Lie tea is an imitation made of dust and sweepings 
of tea or other leaves along with mineral matter of various 
kinds and held together by means of starch or gum. It is 
readily detected by the addition of hot water, when the mass 
breaks down into the fragments of which it is composed. 

The following analyses of spurious teas, received from the 
United States consuls at Canton and Nagasaki (Japan), were 
made by Battershall^' 



17 



I. 2. 3. 4. 

Total ash, 8.62 8.90 7.95 12.58 

Ash insoluble in water, . . . 7.98 6.04 4.95 8.74 

Ash soluble in water, 0.64 1.86 3.00 3.84 

Ash insoluble in acid, 3.92 3.18 1.88 6.60 

Extract, 7.73 14.00 1276 22.10 

Gum, 10.67 7.30 11.00 11.40 

Insoluble leaf, 70.60 70.55 67.00 60.10 

Tannin, 3.13 8.01 1450 1564 

Cafifein, 0.58 none 0.16 0.12 

1 . Partially exhausted and refired tea leaves, known as ' ' Ching 
Suey^^ (clear water), which name doubtless has reference to the 
weakness of a beverage prepared from the article. 

2. "Lie tea," made from Wampan leaves. 

3. A mixture of 10 per cent, green tea and 90 per cent, "lie 
tea," sometimes sold as "Imperial" or "Gunpowder" tea. 

4. "Scented caper tea," consisting of tea dust made up into 
little shot-like pellets by means of "Congou paste" {i. e., boiled 
rice). 

Analytic Methods. 

Water. — This is determined as on page 27. A slight amount 
of caffein may be lost in the drying and counted as water, but 
the error is negligible. 

Ash. — Soluble ash and alkalinity of soluble ash. (See page 

39)- 



TEA 257 

Extract. — 2 grams of the finely powdered tea are boiled for 
an hour in a flask provided with a reflux condenser. The liquid 
is decanted and the residue boiled for a short time with suc- 
cessive portions of 50 c.c. of water until this is no longer colored. 
The solutions are mixed, heated, filtered through- a tared filter, 
to w^hich the insoluble leaf is also transferred. After washing 
with boiling water, the filter and contents are dried to constant 
weight. The extract is determined by difference, or, if desired, 
the filtrate is made up to a definite volume, and an aliquot por- 
tion evaporated and dried at 100° and weighed. 

Nitrogen. — Total and albuminoid nitrogen is determined by 
the methods described on pages 33 and 37. 

Caffein. — This is best determined by Allen's method: 6 
grams of the finely powdered tea and 600 c.c. of water are boiled 
under a reflux condenser for six or eight hours ; 4 grams of lead 
acetate in powder are then added and the liquid again boiled 
for ten minutes. If, on removing the source of heat, the pre- 
cipitate does not curdle and settle readily, leaving the liquid 
colorless or nearly so, a further addition of lead acetate must 
be made and the boiling repeated. When clarification is ef- 
fected, the liquid is passed through a dry filter, 500 c.c. of the 
filtrate (5 grams of the tea) are evaporated to about 50 c.c, and 
a little disodium hydrogen phosphate is added to precipitate 
the remaining lead. The liquid is filtered, the precipitate 
washed, and the filtrate further concentrated to about 40 c.c, 
when the caffein is extracted by at least four agitations with 
chloroform. The separated choroform solutions are mixed, 
and distilled in a tared flask immersed in boiling water. While 
the flask is still hot the last traces of chloroform are removed 
by a current of air, and the residual alkaloid is weighed. 

Determinations of caffein based upon the treatment of the 
leaves with boiling lime water or alkali are valueless, as is also 
the process of Paul & Cownley, in which the leaves are mixed 
with magnesia, dried and exhausted by alcohol. 
23 



258 FOOD ANALYSIS 

The following volumetric method, due to Gomberg, has been 
reported upon favorably by Ladd: 

A weighed quantity of the tea is boiled with water as above, 
the solution made up to a known volume, and filtered. An 
aliquot portion of the filtrate is treated with lead subacetate 
so long as a precipitate is formed. After standing, the pre- 
cipitate is filtered off, the excess of lead carefully removed by 
hydrogen sulfid, the filtrate from the lead sulfid boiled to re- 
move hydrogen sulfid, and divided into two equal parts. One 
portion is acidified with sulfuric or hydrochloric acid and ex- 
cess of decinormal iodin solution added; after standing 5 to 10 
minutes is is filtered and the filtrate titrated with decinormal 
thiosulfate solution. If in the other portion potassium iodid- 
iodin solution (page 26) produces a precipitate, a correction is 
necessary, i c.c. of decinormal thiosulfate corresponds to 
0.00458 gram of caffein. 

Facing. — The coloring-matter used in facing is usually present 
in minute amount, and is best detected by the microscope, the 
leaf being examined by reflected light. A good plan is to shake 
some of the leaves with water, allow the suspended matter to 
settle, and examine the sediment by the microscope and chemic- 
ally. Prussian blue may be distinguished from indigo by the 
fact that the color of the former is discharged by addition of 
sodium hydroxid. Indigo forms a deep blue solution with 
sulfuric acid. Turmeric is detected as on page 73. Graphite 
may be detected by examination under the microscope. 

Added Mineral Matter. — Any considerable addition of 
mineral matter will be shown by the increased proportion of 
ash, which usually ranges from 5 to 6.5 per cent., and only 
in exceptional cases rises to 7.5 per cent. Magnetic iron oxid 
and particles of iron have been found in tea, and may be readily 
separated from it by the magnet. Sand and powdered brick 
have also been found. The former may be accidental. 

Exhausted Tea Leaves. — The detection of admixture of 



TEA 259 

moderate proportion of added tea leaves is difficult. Con- 
siderable addition will be indicated by the decreased propor- 
tion of extract and caffein, and especially of soluble ash and its 
alkalinity. The soluble ash of pure tea is from 2.5 to 4 per cent., 
and is usually over 3 per cent., whereas that of exhausted tea 
is generally not over 0.8 per cent. The alkalinity of the soluble 
ash expressed as potassium oxid is from 1.25 to 2 per cent, (cal- 
culated on the dry tea). In exhausted tea the alkalinity is 
likely to be less than 0.3 per cent. 

The soluble ash is best calculated to percentage of total ash. 
The interference of sand may be eliminated by calculating the 
proportion of ash soluble in water to that soluble in acid. 
Wigner obtained the following average results from the ex- 
amination of 67 samples of tea: 

Siliceous matter, 7.96 per cent. 

Soluble in acid, — 37-54 " ". 

" " water, : S4-5o " " 

Alkalinity of soluble ash, 25.09 " " 

Excluding the portion insoluble in acid, the figures become: 

Soluble in water, 59-21 per cent. 

Alkalinity of soluble ash, 27.26 " " 

If the soluble ash is less than 40 per cent, of the total ash or 
less than 45 per cent, excluding siliceous matter, adulteration 
with exhausted leaves may be suspected. 

The minimum proportion of extract yielded by pure tea is, ac- 
cording to the standard fixed by the Society of Public Analysts 
in 1874, not less than 30 per cent. The proportion usually 
found much exceeds this figure, but congou may contain less. 
The proportion of caffein found by different observers ranges 
from 1.8 to 4 per cent., the lower proportions being found in 
Japan teas. 

Exhausted leaves have in some instances been found to be 
partly unrolled or much frayed and broken, and more posi- 



26o FOOD ANALYSIS 

tive indications might be had by the examination of selected 
leaves of suspicious appearance. 

Foreign Astringents. — Catechu is sometimes added, espe- 
cially to "lie" or ''caper" tea, or to mask the presence of ex- 
hausted leaves. It may be detected by Hager's test: About 
a gram of the sample is boiled with water, the extract treated 
with excess of lead monoxid, and filtered. A solution of silver 
nitrate is added to clear the filtrate; in the presence of catechu, 
a yellow flocculent precipitate, which rapidly becomes dark, 
is formed. Pure tea gives only a slight grayish precipitate of 
silver. Allen recommends the following process, which should 
be applied to the suspected tea, side by side with a genuine sam- 
ple: I gram of the pure tea, and an equal weight of the sus- 
pected sample, are infused in separate p^ortions of loo c.c. each 
of boiling water, and the strained liquid precipitated while 
boiling with a slight excess of neutral lead acetate. 20 c.c. 
of the filtrate from the pure tea (which should be colorless), 
when cautiously heated and treated with a few drops of sil- 
ver nitrate solution, avoiding excess, gives only a very slight 
grayish cloud or precipitate of reduced silver; but the same tea 
containing 2 per cent, of added catechu gives a copious brown- 
ish precipitate, the liquid acquiring a distinctly yellowish tinge. 
With a somewhat larger proportion of catechu, the filtrate from 
the lead precipitate gives a bright green color on adding one 
drop of dilute ferric chlorid, while the solution from pure tea 
gives only a slight reddish color, due to the presence of acetate. 
On allowing the liquid to stand, the adulterated tea gives a pre- 
cipitate of a grayish or olive-green color, the pure tea under- 
going no change. 

Foreign Leaves. — A small proportion of foreign leaves, such 
as those of the rose, jasmine, and orange, are sometimes added 
to impart bouquet, but these are usually removed before pack- 
ing. Other foreign leaves, especially the sloe, willow, elder, 
Chloranthiis inconspicuus, Camellia sasanqua, and Bury a 



TEA 261 

chinensis, have been added in considerable quantity, but the 
practice, so far as concerns the tea shipped to the United States, 
seems to be less common than formerly. The detection of 
such additions is best made by the appearance of the leaf and 
the microscopic examination, but a few chemical tests have been 
proposed which may be of some assistance. Blyth proposes 
to utilize the presence of manganese, which is a constant con- 
stituent of the ash of tea. The suspected leaf is ashed and the 
ash treated on fused platinum foil with potassium nitrate and 
carbonate. The distinct green color due to a manganate is 
readily recognized. Allen has applied the test to various 
leaves and found manganese to be present in the folio w^ing: 
Species of Thea (tea), Camellia sasanqua, C. japonica, coffee, 
beech, blackberry, and sycamore. Manganese was absent 
from the leaves of the hawthorn, ash, raspberry, cherry, plum, 
and rose, and only faint traces were detected in the leaves of the 
Ilex Paraguay ensis, elm, birch, lime, sloe, elder, willow herb, 
and willow. Blyth has also proposed the following test, de- 
pending upon the isolation of caffein and recognition by its 
crystalline form under the microscope: The leaf or fragment 
is boiled for a minute in a watch-glass with a very little water, 
an equal bulk of calcined magnesia is added, and the whole 
heated to boiling and rapidly evaporated to a large-sized drop. 
This drop is transferred to a subliming cell, and if, after heating 
to about 110°, no crystalline sublimate of caffein is obtained, 
the leaf cannot be a tea leaf. If, however, a sublimate of caf- 
fein is obtained, it is not conclusive evidence, since other plants 
contain the alkaloid. 

More satisfactory results are obtained by the examination 
of the shape and venation of the leaf. The sample should be 
softened by soaking in hot water, carefully unrolled, trans- 
ferred to a microscope slide, and examined with a hand lens. 
Such examination will usually be sufficient, but in doubtful 
cases it may be necessary to use higher powers. 



262 FOOD ANALYSIS 

COFFEE 

Cofifee is the seed of species of Cofjea, cultivated in sub- 
tropical climates. The fruit usually consists of two seeds 
surrounded by a pulp, which is removed by fermenting and 
washing. The membranous pericarp removed by machinery 
is sometimes roasted and used as a substitute for coffee. 

The following are the more important constituents of raw 
coffee: An essential oil, fat, caffetannates, caft'cin, and caf- 
fearin. The essential oil has been little studied. The fat of 
coffee is soluble in alcohol, but its composition is not yet clearly 
ascertained. 

Caffetannic acid is crystalline, astringent, soluble in water, 
less soluble in alcohol, and very sparingly in ether. It gives 
a dark green coloration with ferric chlorid, and does not pre- 
cipitate gelatin. 

Coft'ee contains a fairly constant proportion of caffein (see 
page 263). According to Paladino, there is also present a nar- 
cotic alkaloid, which he calls caffearin. Paladino's results 
seem to be corroborated by those of Forster & Riechelmann, 
who found an alkaloid distinguished from caffein by the fol- 
lowing characteristics: failure to respond to the murexid 
test, precipitability by picric acid, and insolubility in chloroform. 

Roasted coffee contains a small amount of sugar, which, 
according to Spencer, consists largely of sucrose. It appears 
to be absent from raw coffee and is derived from the decom- 
position of the glucosids (tannins). 

The aroma of roasted coffee is due to cafjeol, which may be 
separated by distilling with water, agitating the distillate with 
ether, and evaporating. It is an oily liquid, slightly soluble 
in hot water, but easily soluble in alcohol and ether. By fu- 
sion with caustic soda it yields sodium salicylate. The phy- 
siological effects of coffee are attributed to the caffeol, caffein, 
and caffearin. 

The roasting of coffee results in a notable reduction of some 



COFFEE 263 

of the constituents, especially the caffein, fat, and sugar. When 
properly conducted, the total loss in weight amounts to from 
12 to 18 per cent., of which about 8 percent, represents moisture. 
Konig gives the following figures, calculated as percentage of 
moisture-free material: 

Raw. Roasted. 

Soluble in water, 30-93 28.36 

Total nitrogen, 2.21 2.38 

Caffein, i .33 i .42 

Fat, 14-91 16.14 

Sugar, 3.66 1.35 

Fiber, 31-24 25.07 

Other nitrogen-free matter, 34-55 39-^4 

Ash, 3.92 3.87 

. Coffee is sometimes glazed with sugar before roasting. Ac- 
cording to Konig, when so treated it retains much more mois- 
ture. According to Hilger & Juckenack, glazed coffee requires 
to be heated to a much higher temperature, which results in 
about double the usual loss of caffein and fat. 

Raw coffee is subject to less adulteration than roasted and 
especially ground coffee. Coffee beans differ considerably in 
size and quality according to their origin, and the inferior 
kinds are sometimes so treated as to give them the appearance 
of the better qualities. 

West India coffee is for the most part even-sized, pale and 
yellowish, firm and heavy, with fine aroma, losing little weight 
by the roasting process. 

Brazil cojfee is larger, less solid, greenish or w^hite, usually 
styled by the brokers "low" or "low middlings." 

Java coffee is smaller, slightly elongated, pale in color, light 
and deficient in essential oil. 

Ceylon coffee is of all descriptions, but the ordinary planta- 
tion products are even-colored, slightly canoe-shaped, strong 
in aroma and flavor, heavy, and permit of adulteration more 
than other kinds. 



264 FOOD ANALYSIS 

Mocha cojjee is usually considered the best, but very little 
reaches the United States. Porto Rico cofifee is often called 
Mocha. The grains of Mocha coffee are small and dark 
yellow. 

Java coffee, when new, is pale yellow, and is then cheaper 
than when old and brown. This color is partly the effect of 
curing as well as the result of age. 

Java coffee, being of high price, has been imitated by color- 
ing the cheaper grades with dyes or mineral pigments. 

According to Waller, Java coffee is imitated by exposing 
South American coffee to a high moist heat, by which the color 
is changed from green to brown. 

Raw coffee is heavier than water. Fade gives the specific 
gravity of raw coffee berries at from 1.041 to' 1.368. Dam- 
aged coffee that has been washed and partially roasted to im- 
prove the color may have a specific gravity less than i . Roasted 
coffee has a specific gravity of from 0.500 to 0.635, but samples 
that have been made to take up much water by steaming and 
then coating with glycerol or sugar (see page 263) may possess 
a specific gravity appreciably higher (0.650 to 0.770). Implicit 
reliance should not be placed on these figures, since over- 
roasted coffees may be heavier than water. The specific gravity 
of raw coffee may be determined by immersing the beans in 
strong brine and cautiously adding water until they remain 
suspended in the liquid. The specific gravity of the liquid is 
then determined as usual. In the case of roasted coft'ee the 
brine is replaced by petroleum spirit to which is gradually added 
ordinary petroleum. 

Adulteration with exhausted coffee beans is reported by 
Roos. The samples examined yielded only i per cent, of ether 
extract. 

Facing. — The following are reported to have been used as 
"facing" for coffee. Scheele's green, chrome yellow, ochre, 
silesian blue, burnt umber, Venetian red, charcoal, indigo. 



COFFEE 265 

ultramarine blue, clay, gypsum. A blue color is also said to 
be produced by shaking the beans with finely powdered iron. 
The beans are sometimes polished by rotating in a cylinder 
with soapstone. 

The examination for facing should be made with the micro- 
scope, and also by shaking with water, and examining the 
sediment, as described under tea (page 258). Artificial colors 
may usually be detected by treating the beans with strong 
alcohol, evaporating to dryness, and testing the residue (see 
pages 64 and 66). 

Imitation beans have frequently been sold for use in mixing 
with coffee. In some cases these are molded in close imita- 
tion of the true beans. The material used for the purpose is 
sometimes clay, but more frequently one or more of the fol- 
lowing: Wheat flour, chicory, bran, rye, peas, and acorns. 
These are often mixed with molasses. Ferrous sulfate has also 
been found. 

Most imitation coffee is heavier than water, but the readiest 
means of detection is by means of the microscope, the appli- 
cation of the iodin test for starch, and determination of the ash. 

Many substances have been used as substitutes for coffee as 
well as for its adulteration; among these are chicory, Mogdad 
and Mussaenda coffee, roasted cereals and leguminous seeds, 
cocoa husks, and figs. 

Coffee contains no starch, a constituent of many adulter- 
ants, such as cereals and acorns. It may be detected by Allen's 
method: The coffee is boiled for a few minutes with about 
ten parts of water. When the liquid has become perfectly 
cold, some dilute sulfuric acid is added, a strong solution of 
potassium permanganate is dropped in cautiously, with agita- 
tion, until the coloring-matter is nearly destroyed, when the 
liquid is strained or decanted from the insoluble matter and 
iodin added. A distinct reaction occurs in the presence of 
even i per cent, of starch. In identifying the starch granules 
24 



266 



lOOD ANALYSIS 



hp--- 



- qu 



with the microscope it is advisable to make a preliminary ex- 
traction of the sample with ether, and subsequently with alcohol. 
Chicory is the root of the Cichorium intybus L. Its micro- 
scopic structure distinguishes it from colTee. The cells of the 
parenchyma are large, smooth-walled, and regular. The milk 
ducts are branched and filled with a coarsely granular material. 
The body of the root contains long, pointed cells presenting a 

characteristic dotted appear- 
ance. (See Fig. 48.^*^) It 
contains no starch. Dande- 
lion and other sweet roots 
present a somewhat similar 
structure, but the ducts are 
scaliform, the cells larger, 
and milk vessels are absent. 
Rimmington recommends 
the following method for the 
detection of chicory: The 
sample is boiled for a short 
time with water containing 
a little sodium carbonate; 
the solution is decanted and 
the residue treated with a 
solution of bleaching pow- 
der for several hours, when 
decolorization will be ef- 
fected. The coffee will be 
found as a dark stratum at the bottom of the beaker and the 
chicory as a light stratum above it. 

Analytic Methods. — The following preliminary tests may 
be of value. A small quantity of the ground material is sprin- 
kled on cold water. Coffee will usually float, and impart very 
little color to the water. Chicory and most other additions sink, 
and the caramel contained in them dissolves quickly, forming 




Fig. 48. 

5', Vascular tissue; ^/», parenchyma ; /, 

fibers; ;;/, medullary rays. 



COFFEE 267 

a dark and usually turbid solution. Coffee grains are hard, 
whereas chicory and some other adulterants, after maceration 
for some hours in water, are quite soft. At the end of this time 
if the mixture be transferred to a piece of stretched cloth and 
rubbed with a pestle, the chicory will pass through. 

The proportion of the adulterant which has been detected 
by the microscope or the preliminary tests just mentioned may 
often be determined with a fair degree of accuracy by chemi- 
cal examination, especially by the determinations of fat, caf- 
fein, water extract, and ash. 

The actual amount of coffee present may be determined by 
calculation from the caffein present determined by the process 
given on page 257, using double the quantity of material. 

In the presence of chicory the extracted alkaloid is liable to 
be strongly colored, and Allen recommends that it be redis- 
solved in water, a few drops of sodium hydroxid added, and 
the liquid again extracted with chloroform. 

Caffetannic acid may be determined by Krug's method*^: 2 
grams of the material finely powdered is digested for 36 hours 
with 10 c.c. of water at a moderate temperature, then 25 c.c. 
of 90 per cent, alcohol added and the digestion continued for 
24 hours. The liquid is filtered and the precipitate washed 
with 90 per cent, alcohol. The filtrate is heated to boiling, 
and a boiling concentrated solution of lead acetate added. 
When the precipitate (lead caffetannate) has become floccu- 
lent, it is separated, washed on the filter with alcohol (90%), 
until the washings are free from lead (ammonium sulfid being 
used as a test), and then with ether, until free from fat. It is 
dried at 100° and weighed. The weight multiplied by 0.516 
gives the caffetannic acid. 

The proportion of caffein in roasted coffees, ranges from 0.8 
to 1.3 per cent. In the better grades it probably does not go 
below I.I per cent., 1.2 might be taken as a basis of calcula- 
tion. 



268 FOOD ANALYSIS 

Fat. — The fat of coffee may be determined by extracting 
with petroleum spirit or carbon tetrachlorid the material dried 
at 1 00°. According to Macfarlane, the petroleum spirit ex- 
tract from previously dried cofifee usually ranges from 10 to 12 
per cent. Only one sample out of nearly fifty showed less than 
10, and 12.5 per cent, was reached only in a few cases. 

Water- extract. — Valuable indications are often furnished by 
the determination of the amount of water-extract, which is 
fairly uniform and little affected by the usual variations in ex- 
tent of roasting. The determination is simplified by the ob- 
servation of the specific gravity of the solution in water as 
recommended by Graham, Stenhouse, and Campbell. One 
part of the sample is treated with ten parts of water, the liquid 
heated to boiling, cooled to 15.5°, and the specific gravity taken. 
The following figures were obtained in this manner: 

Mocha coffee, 1008.0 Turnips, 102 1.4 

Neilgherry coffee, 1008.4 Dandelion, 102 1 .9 

Plantation Ceylon coffee, 1008.7 Red beet, 1022. i 

Native Ceylon coffee, 1009.0 Marigold wurzel, 1023.5 

Java coffee, 1008.7 Lupins, 1005.7 

Jamaica coffee, 1008.8 Peas, 1007.3 

Costa Rica coffee, 1009.0 Beans, 1008.4 

" average, 1008.7 Bro^vn malt, 1010.9 

{1019.1 Black " 1021.2 

to Rye meal, 102 1 .6 

1023.6 Maize, 1025.3 

" average, 102 i.o Bread raspings, 1026.3 

Parsnips, 1014.3 Acorns, 1007.3 

Carrots, 1017.1 Spent tan, 1002. i 

According to McGill, the specific gravity of the infusions of 
coffee and chicory are materially aft'ected by the fineness of 
powder and the time occupied in heating the solution to boiling, 
and the duration of the boiling. He recommends the following 
process: 10 grams of the dried, finely powdered sample are 
heated with loo c.c. of distilled water in a flask provided with 
a reflux condenser. The heat is adjusted so that ebuUition 



COFFEE 269 

commences in 10 to 15 minutes, and the boiling continued for 
exactly one hour; the liquid is allowed to stand for 15 minutes, 
and then passed through a dry filter. The average specific 
gravity of the decoction from pure coffee was found to be 
1009.86 at 17°, and that of chicory, 1028.21. The amount of 
coffee present in a mixture of coffee and chicory may be 
approximately calculated by deducting the observed gravity 
from 1028.21 and multiplying the remainder by 5.45. 

Macfarlane has determined the water extract by boiling 
with water the dried residue from the determination of fat 
(page 268) and redrying and weighing the residue. The 
water-extract is determined by difference. The following 
results were obtained : 

Coffee (Santos, Mocha, and Java), 20.4-22.4 per cent. 

Chicory, 77.7 " " 

Hehner has found highly roasted chicory to give a water- ex- 
tract as low as 54.1 per cent, and a specific gravity of the 10 
per cent, solution of 1019. 

Cassal has found genuine coffee to give a water-extract as 
high as 29 per cent. More recently several observers have 
called attention to the fact that the proportion of water-soluble 
matter in commercial chicory may be markedly greater than 
that found in the above samples, examined years ago. This 
appears to be due, as pointed out by Dyer, to the less roasting 
to which it is subjected. The following results, due to Dyer, 
were obtained by boiling the sample with water, washing, dry- 
ing, and weighing the insoluble residue, and determining the 
soluble matters by difference. The moisture varied in extreme 
cases from i to 4 per cent., but the results were calculated 
as percentage of the dried material : 



270 FOOD ANALYSIS 

Insoluble Ash 

IN Ethek- NiTKO- Total Soluble in 

Water. extract, gen. Ash. Water. Sand. 

Chicory "nibs" described as 

"medium roast," 22.40 2.57 1.53 4.63 2.50 0.70 

Chicory "nibs" described as 

"dark roast," 50.30 2.43 1.67 4.70 2.99 0.30 

21.50 1.90 1.23 5.33 1.60 0.77 



Ground chicory, 9 samples, . -{ to to to to to to 

37.80 3.87 1.52 8.23 3.30 3.97 

In eight out of the eleven samples the matter insoluble in 
water ranged from 21.50 to 23.50 per cent. One sample con- 
tained 35.50, one 37.80, and one 50.30 per cent. 

Graham, Stenhouse, and Campbell have suggested the tinc- 
torial power of the infusion as a means of determining adul- 
terants in coffee. As a rule, the coloring power of chicory is 
about three times as great as that of coffee. The method 
may be useful in the detection of added caramel or of added 
sugar which has been caramelized in roasting. The infusion 
should be compared with that from pure coffee. 

The ash of coffee is usually 3.5 to 4.5 per cent., and rarely, 
if ever, 5 per cent. Of this, about 80 per cent, is soluble in 
water. It contains mere traces of silica, and is almost in- 
variably white. A red ash usually indicates adulteration. A 
notable amount of potassium is present, but sodium may be 
present in small amount. Analyses by Ludwig indicate that 
the composition of coffee ash is subject to marked variation 
according to soil. Chicory contains about 6 per cent, of ash, 
of which only from 30 to 40 per cent, is soluble in water. It 
may contain several per cent, of silica and usually carries con- 
siderable admixed sand. Sodium is always present, often to a 
considerable extent. 

The ash of cereals and leguminous seeds, is usually less than 
that of coffee (see page 95). 

The following table, due to Konig, gives some results ob- 
tained from the examination of various coffee adulterants: 



COFFEE 



271 



Nitro- 
genous 
Water. Matter. 

Chicory, roasted, ..13.16 6.53 

Figs, roasted, 12.50 4.57 

St. John's bread 

(carob bean), ... 5.35 8.93 

Cereals (rye, etc.),.. 1 2. 50 12.15 

Malt, 7.08 13.05 

Mogdad coSec(Cas- 

sia occidentalis),. 11. og 15.13 
"Congo" coffee, 

raw, 13-72 39.82 

"Congo" coffee, 

roasted, 4.22 27.06 

Acorns, shelled and 

roasted, 12.50 6.78 

Date stones, 9.27 5.46 

Fruit of wax palm, 

raw, 9.37 6.54 

Fruit of wax palm, 

roasted, ., 3.76 6.99 











Water- 










extract 










Calcu- 










lated 


Ether- 








ON THE 


ex- 


N-free 






Dry Ma- 


tract. 


Sugar. Matter. 


Fiber. 


Ash. 


terial. 


2.74 


17.89 41.42 


12.07 


6.19 


70.50 


2.96 


32.50 31.92 


12.34 


5-21 


82.50 


3-65 


69.83 


10.15 


2.09 


63.71 


3-57 


4.12 55.66 


8.45 


3-55 


48.53 


2.25 


15-67 51-74 


7-38 


2.83 


65.00 


2-55 


46.69 


21.21 


4.33 


30.00 


1.26 


37-09 


4.41 


3-70 




1. 19 


3-25 39-74 


19.28 


4.63 


22.50 


4-35 


69.27 


5.02 


2.07 


28.88 


8.50 


52.86 


23-97 


1.44 


12.87 


IO-57 


1.67 25.48 


44.31 


2.06 


13-41 


14.06 


1-25 33-25 


38.45 


2.24 


14.03 



A number of methods have been proposed for the deter- 
mination of the caramel in coffee roasted with sugar. A 
method due to Hilger is as follows: 10 grams of the whole 
coffee are shaken for half an hour each time with three suc- 
cessive portions of 100 c.c. of a mixture of equal parts of water 
and 85 per cent, alcohol. The united solutions are made up 
to 500 c.c, filtered, the residue dried at 100°, weighed, and the 
ash determined and deducted. It is necessary to decant the 
liquid from the berries before filtering, since the extra time 
considerably increases the relative amount of ash in the extract, 
due to the more complete extraction of the constituents of the 
berry itself. Fresenius & Griinhut consider that the best 
results are had by deducting from the result a mean constant 
for the materials extracted from the coffee itself. 

The following results were obtained. The roasting of the 



2 72 



FOOD ANALYSIS 



coffee without sugar was performed in the normal manner; 
/. e., the loss on roasting was about i8 per cent. : 

Soluble Residue 
(Less Ash). 

Yellow Java, 0.71 

Green " 0.62 

Blue " 1.39 

Maracaibo, 0.60 

Average, 0.83 

Percentage of Ash- 
free Soluble Matter 
Less 0.83. 

Yellow Java roasted with 7^ per cent, of sugar, 2.21 

" 9 " " 2.83 

" 7* " " 2.06 

" 9 " " 3.46 

" 7i " " 2-55 



Green 

Blue 

Maracaibo 



9 

7* 

9 

7i 

9 

7h 

9 



.4.00 
.2.78 

■3-39 



Coffee Extracts. — Many attempts have been made to pre- 
pare a concentrated infusion of coffee, but the results have 
not been satisfactory. In most cases preservatives are neces- 
sary. Some preparations contain excessive proportions of 
sugar, and occasionally caffein is added to enrich the mixture. 
Moor & Priest give the following analyses of English prepara- 
tions: 



Total Solids. Ash. 

Coffee extract, 39.9 4.25 

27.9 0.95 

" " with chicory, 30.0 0.36 

34.8 1.28 

46.4 0.43 

" " with chicory, 37.6 0.36 

" 50-6 0.55 

" " with chicory, 48.6 1.87 

" sugar, 51.5 2.50 

" " " chicory, 48.5 1.14 



Nitrogen. Caffein. 
0.96 1.98 



0.15 

0.23 
0.06 

0.41 

0.37 
0.38 
0.30 



0.47 
0.32 
0.54 

0-57 
0.02 
0.56 
0.26 
0.61 
0.28 



In the first sample caffein has probably been added. 
Essence of Cofjee. — Coarsely broken cereals roasted with 



CACAO AND CHOCOLATE 273 

molasses have sold under this title. The nature of the material 
may usually be determined by simple inspection. Of late years, 
the term '^ essence for coffee" has been substituted. 

The starch in the original material will be somewhat changed 
both in chemical and physical characteristics, but the reaction 
with iodin and the microscopic characters will generally assist 
in the recognition of the cereals present. 

CACAO AND CHOCOLATE 

Cacao is prepared from the seeds of Theohroma cacao L. The 
fruit contains from 25 to 40 slightly ovate flattened seeds, 1.5 
to 2.5 cm. long and 0.6 to 1.5 cm. broad, which are colorless 
when first removed from the pulp, but become yellow, red, or 
brown on exposure. They are dried in the sun, either at once 
or after being subjected to fermentation (brought about in 
some cases by burial), which removes the pulp and much of the 
acridity and bitterness. 

Cacao seeds contain theobromin, caffein, fat, tannin, starch, 
gum, proteids, and tartrates. The taste and odor are due to 
volatile materials developed in roasting. 

Theobromin, dimethylxanthin, crystallizes in colorless, 
minute, rhombic needles. One part is soluble in the following 
parts of solvents: cold water, 1600; boiling water, 148; cold 
alcohol, 4280; boiling alcohol, 400; cold ether, 1700; boiling 
ether, 600; boiling chloroform, 105. It is insoluble in petro- 
leum spirit. It dissolves in acid and alkaline solutions, especially 
in ammonium hydroxid, and is completely extracted from alka- 
line solution by chloroform. When the solution in ammo- 
nium hydroxid is mixed with silver nitrate and heated for a 
considerable time, a silver compound is precipitated. 

Kunze has examined the methods for the separation of the 
alkaloids, and found all defective. In estimating the alkaloids 
of cacao previous removal of the fat is not advisable, as some 
alkaloid is extracted. Kunze recommends the following process : 



2 74 FOOD ANALYSIS 

The nialcrial is boiled for 30 minutes with normal sulfuric 
acid, filtered, and a large amount of a solution of sodium 
phosphomolybdate in nitric acid added. The precipitate, 
which usually settles rapidly, is removed by filtration after 24 
hours, washed with dilute sulfuric acid, and at once decom- 
posed by treatment with barium hydroxid solution, the excess 
of barium hydroxid being removed by carbon dioxid. The 
liquid and precipitate are evaporated to dryness and the residue 
extracted with boiling chloroform. The chloroform solution, 
on evaporation, leaves the alkaloids almost perfectly pure, and 
containing only a trace of ash. 

Sodium phosphomolybdate solution is prepared as follows: 
A warm solution of disodium hydrogen phosphate is acidu- 
lated with nitric acid and an excess of ammonium molybdate 
solution added. The precipitate is washed with water con- 
taining nitric acid and dissolved in a hot solution of sodium 
carbonate. The liquid is evaporated to dryness, the residue 
ignited at a low red heat until all ammonium is volatilized, 
moistened with nitric acid, and again ignited, i gram of the 
product is dissolved in 10 c.c. of water and i c.c. of nitric acid 
(sp. gr. 1.42) added. 

Separation of the alkaloids may be effected by converting 
the theobromin into a silver compound. The mixture of alka- 
loids is dissolved in ammonium hydroxid, a considerable ex- 
cess of nitrate is added, the solution boiled down to small bulk, 
and until all free ammonia is expelled. The crystalline pre- 
cipitate is collected, washed with boiling water, ignited, and 
the metallic silver weighed. The process may be made volu- 
metric by titrating the excess of silver in the filtrate by Vol- 
hard's method. In the latter case the alkaloids may be readily 
isolated from the precipitate and the filtrate (after titration), 
and tested as to their purity, identity, etc. The separation 
of caffein from theobromin by means of benzene is imperfect. 

The proportions of theobromin given by different observers 



CACAO AND CHOCOLATE 275 

differ greatly, owing in part to the methods employed. The 
average of the reported data is about 1.5 per cent. Kunze 
found by his method 1.2 per cent, total alkaloids. Weigmann 
obtained the following results: 

Beans. Husks. 

Theobromin, per cent., 1.26 0.50 

Cafifein, percent., 0.17 0.15 

According to Stutzer, the nitrogenous constituents of cacao 
are of three types: 

1. Non-proteids, not precipitated by copper hydroxid (the- 
obromin, caffein, and amido-compounds). 

2. Digestible albumin, insoluble in pure water in presence 
of copper hydroxid, but soluble when treated successively with 
acid gastric juice and alkaline pancreatic extract. 

3. Insoluble and indigestible nitrogenous matter. 

He gives analyses of three samples, showing the relative pro- 
portion of these forms : 

Nitrogen as soluble compounds, in- 
cluding that of alkaloids, 31-43 26.95 29.79 

Nitrogen as digestible albumin, 33-34 40.61 22.62 

Nitrogen as indigestible matter, 35-33 32-44 47-83 



100.00 100.00 100.00 



Fat. — The so-called cacao-butter is a yellowish-white solid, 
of pleasant odor, melting between 28° and 30°. Further data 
in regard to it are given in connection with the fats. 

Cacao-red. — This appears to be an oxidation product of the 
tannin. It does not exist as such in the cacao. It may be 
prepared from the aqueous or alcoholic decoction by pre- 
cipitating with lead acetate and decomposing the washed pre- 
cipitate with hydrogen sulfid. The colorless liquid so obtained 
becomes red on evaporation. Cacao-red is slightly soluble in 
cold water, much more so in hot. 

Gum. — About 2 per cent, of gum resembling gum arabic is 



276 



FOOD ANALYSIS 



present. It is ])rccipitatc(l by alcohol from the watery extract 
of the fat free cacao. It is dextrorotatory. 

Tartaric Acid. — This has been found to be present to the 
extent of .several per cent. Weigmann estimates it by neu- 
trahzing the aqueous extract with ammonium hydroxid, add- 
ing calcium chlorid, redissolving the precipitate in hydro- 
chloric acid, and reprecipitating with sodium hydroxid. From 
4.34 to 5.85 per cent, of tartaric acid were found in this way. 

Starch. — The granules of cacao-starch are very small; their 
microscopic characters are given on page 90. Samples of cacao 
examined by Ewell contained from 5.78 to 15.13 per cent, of 
starch. 

Mineral Matter. — The ash of cacao consists largely of phos- 
phates with but little chlorids and carbonates. The amount 
of magnesium exceeds notably that of the calcium. The pro- 
portion of sodium is small, and traces of copper are usually 
present. The proportion of husk ranges from 8 to 15 per cent. 

ANALYSES BY J. BELL 





Per 100 OF 
Cacao. 


Per 100 OF Ash. 




Water. 


Ash (on 
Dry 
Sub- 
stance). 


Soluble 

in 
Water. 


Insol. 

in 
Acid. 


Phos- 
phoric 
Oxid. 


Carbon 
Dioxid. 


Potas- 
sium 
Oxid. 


Fer- 
rous 
Oxid. 


Guayaquil nibs (/. 
<f. , huskedj, . . 

Surinam nibs, . . 

Grenada nib.s, . . 

Finest Trinidad 
nibs, ..... 

Finest Trinidad 
husks, .... 


5.06 
4-55 
571 

4-47 
10.19 


3(>3 
2.90 
2.82 

2.75 
8.63 


56.3 

43.5 
48.6 

46.6 
54-9 


None 
None 
None 

None 

5.9. 


49.4 
378 
39-2 

36.2 


0.69 

331 
2.92 

4.19 

10.8 


23-4 
28.0 
27.6 

293 
37-9 


0.21 
0.38 
0.15 

0. II 
0.63 



The important commercial cacao preparations are : 

Plain chocolate J which consists of the roasted and husked 



CACAO AND CHOCOLATE 



277 



seeds, ground to a paste while quite hot and pressed into cakes. 
This is known in Europe as "cacao masse." 





ANALYSES 


BY H. 


WEIGMANN 








Mois- 
ture. 

• 


Nitro- 
genous 
Matter. 


Thro- 

BROMIN. 


Fat. 


Starch. 


Other 

NlTRO- 

gen-free 
Matter. 


Fiber. 


Ash. 


Raw, unhusked, 


7-93 


14.19 


1-49 


45-57 


5.85 


17.07 


4.78 


4.61 


Roasted, " 


6.79 


14-13 


1.58 


46.19 


6.06 


18.04 


4-63 


4. 16 


*' husked 


















(nibs), . . . 


5-58 


14-13 


1-55 


50.09 


8.77 


13-91 


3-93 


3-59 


Cacao masse, 


















(plain choco- 


















late), .... 


4.16 


13-97 


1.56 


53-03 


9.02 


12.79 


3-40 


3-^3 


Husks (contained 


















4.06 per cent. 


















sand), .... 


11-73 


13-95 


073 


4.66 


43-29 


16.02 


10.71 



Sweet chocolate is the mixture of the above with 50 per cent. 
or more of sugar, and flavoring materials, such as spices and 
vanilla. 

Cacao essence, or cacao powder, is prepared by removing 
from the husked and roasted bean, by means of heat and pres- 
sure, a portion (usually about one-half) of the fat. 

The so-called soluble "cocoas" are prepared by treating the 
above with ammonium hydroxid, sodium or potassium carbon- 
ate, or steam to destroy the cellular structure, to convert the pro- 
teids into more soluble modifications, but more especially to 
emulsify the fat so that it may not come to the surface when 
the decoction is made. The treatment with alkaline carbonate 
is practised by the Dutch manufacturers. The term soluble in 
connection with such preparations is not accurate, as is evident 
from the following analyses made by Stutzer: 

I. Made from a mixture of Ariba, Machala, and Bahia 
cacao without the use of chemicals. 

II. Dutch cacao. 



278 



FOOD ANALYSIS 



III and I\\ German cacao prepared, in Stutzer's opinion, 
by the use of ammonium hydroxid. 

I. 

Water, 4.30 

Fat, 27.83 

Fiber, 3.36 ) 

Nitrogen-free extract, 38.62 ) 

Total nitrogenous substances (i), 20.84 

Ash (2), 5.05 

(i), Total nitrogen, 3.68 

Theobromin, i .92 

Ammonia, 0.06 

Amido-compounds, 1.43 

Digestible albumin, 10.25 

Indigestible nitrogenous matters, . 7.18 

Containing nitrogen, 1.15 

Proportion of total nitrogen indi- 
gestible, 31.2 

(2) Phosphoric oxid, i .85 

" " soluble in water, 1.43 
Ash soluble in water, 3.76 

Stutzer considers that the addition of alkalies is unneces- 
sary, since the good results may be had from the untreated 
bean, if the preparation and roasting be properly conducted. 
U. S. Standard. 
Plain or hitter chocolate. 

Ash insoluble in water, not over . 3.0 per cent. 
Crude fiber " '' 

Starch " " 

Cacao-fat not less than .45.0 

Sweet chocolate and chocolate coatings are plain chocolate 
mixed with sugar (sucrose), with or without the addition of 
cacao butter, spices or other flavoring materials, and contain 
in the sugar-free and fat-free residue no higher percentage of 
either ash, fiber or starch than is found in the sugar-free and fat- 
free residue of plain chocolate. 



II. 


III. 


IV. 


i-^i 


6.56 


5-41 


30-51 


27-34 


33-85 


3748 


39-99 


36.06 


19.88 


20.93 


19-25 


8.30 


5-i8 


5-43 


2>-3o 


3-95 


3-57 


1-73 


1.98 


1.80 


0.03 


0.46 


o-U 


1-25 


0.31 


1-31 


7.68 


10.50 


7.81 


9.19 


7.68 


8.00 


1.47 


1-23 


1.28 


44-5 


32.2 


35-8 


2.52 


2.14 


2.05 


0.50 


0.74 


0.77 


4.76 


2.86 


2.76 



0- 

3-5 
9.0 



CACAO AND CHOCOLATE 279 

Cacao or powdered cacao is cacao nibs, with or without the 
germ, deprived of a portion of its fat and finely pulverized, and 
contains percentages of ash, crude fiber and starch corresponding 
to those in chocolate after correction for fat removed. 

Sweet or sweetened cacao is cacao mixed with sugar (sucrose) 
and contains not more than 60 per cent, of sugar (sucrose), and 
in the sugar-free and fat-free residue no higher percentage of 
either ash, crude fiber, or starch than is found in the sugar- 
free and fat-free residue of plain chocolate. 

Adulterations. — The finest grades of cacao are made from 
the cotyledons only. The husks are occasionally added to the 
cheaper grades of chocolate. On account of the large pro- 
portion of a fat in cacao (usually about 50 per cent.), it is im- 
possible to prepare from it a permanent powder unless a part of 
the fat be removed or a diluent such as starch or sugar be added. 
In many cases more than half of the fat is allowed to remain. 
The common adulterants of cacao powder are sugar, starches, 
and flours. The color of the diluted material may be improved 
by the addition of brown iron oxid or artificial colors. Cop- 
per sulfate, potassium chromate, and nickel sulfate are said to 
have been added. Chocolate is often adulterated with ground 
peanuts, almond cake, and similar material. In some cases 
a portion of the fat is removed and foreign fat substituted. 
Finely divided tin is stated to have been added in order to im- 
part a metallic luster. 

Analytic Methods. — A careful examination under the 
microscope should be made in order to determine the pres- 
ence of husks, foreign starches, peanut, almond, or other ad- 
ditions. A determination of the ash, and of its solubility and 
alkalinity, should be made. The ash of pure cacao is white, 
and usually under 4 per cent., if prepared from tlic cotyledons 
only. A higher proportion may point to the presence of husks, 
added mineral matter, or the use of alkali in the manufacture. 



28o FOOD ANALYSIS 

(See tables, pp. 27 and 41.) The moisture and fat should be 
determined as on pages 278 and 282. The extraction of the fat 
should be performed by means of petroleum spirit. The 
material extracted may be examined for foreign fats as described 
on page 1 79. In the case of cacao prepared by the use of alkali 
an appreciable amount of soap will be present, which will re- 
main undissolved by the petroleum spirit. It may be separated 
by treating the residue with alcohol acidified with hydro- 
chloric acid, evaporating to dryness, and shaking with water and 
ether. The fatty acids are recovered from the ether by evapora- 
tion. 

The determination of the theobromin and caffein may be 
made as described on page 273. The determination of total 
nitrogen is easier. The following analyses by Bitterj'st show 
the use of such determination: 

Percentage of Proteids. 

Pure chocolate, 9.10 

" cacao, 1 7-57 

Peanuts, 28.18 

Peanut-cake, 46.90 

Pure chocolate -|- 10 per cent, of peanuts, 12.53 

" " + 10 " peanut-cake, i5-7o 

" cacao + 10 " " 21.18 

Sugar. — Exact determinations of sugar are difhcult, but 
approximations quite sufficient for practical purposes may be 
made by the polarimeter. The gum introduces an error rang- 
ing from 0.3 to 2.0 per cent. To avoid interference from starch, 
the solution must be made with cold water. Ewell has found 
that it is necessary to use about 40 c.c. of water for each 
gram of sample. The following process, described by Ewell, 
is adapted to a polarimeter requiring a concentration of 26.048 
grams: 13.024 grams of material are triturated with alcohol to 
a smooth paste, which is transferred to a 500 c.c. flask, diluted 
with 400 to 450 c.c. of water, and shaken occasionally during four 



CACAO AND CHOCOLATE 281 

hours; after which lo c.c. of a saturated solution of lead acetate 
are added, the volume brought to 500 ex., and allowed to stand 
for one hour, with occasional shaking. The solution is filtered 
and the polarimetric reading taken. If a 200 mm. tube is used 
the reading, multiplied by 10, will give results close enough, 
since there is, as noted above, an indefinite error from the gum 
in solution. Ewell prefers to allow for the volume of the pre- 
cipitate, and has given a formula which, reduced to a simpler 
form than as he presents it, is, for the 200 mm. tube : 

Percentage of sugar = 9.76 R + 0.0130 R^; R being the observed reading. 

Starch. — This is determined by the method given on page 93, 
the sugar being first removed by cold water. 

Crude Fiber. — This is determined as on page 38. Little 
reliance can be placed upon many published figures for this 
datum, on account of the differences in methods employed. 

Alkalies. — For detecting the use of alkalies in the manu- 
facture of cacao the following data may be determined : Total 
ash, water-soluble ash, total phosphate and that in the cold 
water solution, expressed as phosphoric oxid. The relative 
proportions of these constituents in the ash of normal cacao 
and of cacao treated with fixed alkalies and ammonia are given 
in the table on page 278. Additional evidence of the use of 
ammonia is obtained by distillation of the sample with mag- 
nesia and determination of the ammonia in the distillate. 
If this process yields more than o.i per cent, of nitrogen in 
the form of ammonia, Stutzer considers the result certain evi- 
dence of the use of ammonia or ammonium salts in the manu- 
facture. 

The following table gives some of the results obtained by 
Ewell from an examination of cacao preparations as found in 
the American market: 



25 



282 



FOOD ANALYSIS 



Plain Chocolates 
Chocolate, 



Sxveet Chocolates : 

"Instantaneous 
Chocolate," . 

"Powdered," . 

" Princess," , . 

"Vanilla," . . 



Foreign ,,, ^ 

Starches. Water Fat. 



None. 

Much wheat 
starch. 

Much wheat 
flour. 



None. 
None. 
None. 
None. 



Cocoas and Bromas: 

Breakfast Cocoa, None. 

Cocoa Extract, . None. 

Dutch Cocoa, . None. 

Breakfast Cocoa, ; Wheat flour 
I and arrow- 
root. 

Prepared Cocoa, Much arrow- 
root. 



3.18 ! 50.84 
3.09 49.81 
3.82 49.40 



1.88 

1-55 
1.46 

0.65 



24.04 

17-73 
25- 74 
22.49 

25.83 

30.95 
31.48 

35-85 
25 -94 



Cane- 
sugar ' Crude Total 
BY Fiber. Ash. 
Polar. 



c.c. 

2-91 3-44 : 2 55 



— Acid 
10 

Req. to 
Neu- 
tral- 
ize 
Ash of 
iGram. 



• • 


2.63 


3.0S 


2.12 


■ • 


2.74 


3.18 


2.30 


53 


1.32 


1.69 


1-45 


65 


0.94 


1. 21 


0.75 


55 


1. 14 


I 54 


0.92 


57 


1.23 


1.52 


I. GO 


. . 


4.23 


505 


3.65 


• • 


389 


4.24 


2.9 


• • 


376 


6.06 


4.8 




308 


384 


2.6 


26 


1.51 


3- 15 


1-3 



CONDIMENTS AND SPICES 

VINEGAR 

Vinegar is the acid liquid resulting from the acetous fer- 
mentation of various decoctions or fruit juices. Acetic acid 
is the prominent constituent, but small amounts of alcohol, 
aldehyde, and ethyl acetate are usually present, together with 



VINEGAR 2 S3 

extractive matters depending upon the nature of the material 
used. Very dilute solutions of acetic acid do not keep well, 
and a little alcohol is regarded by some persons as desirable, 
improving the flavor and keeping qualities. Some mineral 
acid was formerly thought to be necessary as a preservative. 
Such addition is not needed, but is sometimes practised as an 
adulteration. Sulfuric acid is usually employed, rarely hy- 
drochloric. -^ 

Vinegar is often made by spontaneous fermentation, but 
malt and spirit vinegars are mostly made by passing dilute 
alcohol over shavings impregnated with the acetic ferment, 
a regulated supply of air being maintained at the same time. 
The conversion of the alcohol into acetic acid is rapid. 

Wine, cider, malt, and spirit vinegar are the chief forms. 

Wine Vinegar. — That from white wine is most esteemed. 
It usually contains between 5 and 10 per cent, of acetic acid, 
1.5 and 3 per cent, of solids, and 0.2 and 0.6 per cent, of ash. 
The extract contains from 0.25 to 0.5 per cent, of acetic potas- 
sium tartrate. The following analyses of true vinegar result- 
ing from four months' fermentation are by Farnsteiner: 

I. 2. 3. 

Alcohol, 3.75 0.00 1.23 

Acid, 3.56 7.60 6.00 

Solids, 2.03 3.64 2.56 

Ash, 0.28 0.30 0.34 

Alkalinity of ash in c.c. of normal alkali, ... 1.78 2.90 2.85 

Small amounts of sugar, glycerol, and tartaric acid are pres- 
ent in each sample. 

U. S. Standard. 

Acetic acid not less than ..4 grams in 100 c.c. 

Grape solids " " " ..1.4 

Grape ash " " " . .0.13 

In the United States, spirit vinegar made from the dilute 
alcohol called ''low wine" is often sold as white wine vinegar. 



(( u II ^ . a a ii 

• -1-4 

U ii ^ -, ^ " ii ii 



284 FOOD ANALYSIS 

Cider vinegar is a brownish liquid containing about 4 per 
cent, of acetic acid and 2 per cent, of solid matter which has 
the odor and taste of apples. It is frequently imitated by spirit 
vinegar or diluted acetic acid colored with caramel. G. S. 
Cox and A. W. Smith have published analyses of commer- 
cial cider vinegars. The former found in 20 samples a per- 
centage range of acidity from 2.3 to 8.4, solids 1.34 to 4, ash 
0.25 to 0.52. Smith examined 51 samples, 22 of which were 
genuine, 27 diluted with water or spirit vinegar, one made from 
dried apples and glucose, and one made from cider and grape- 
juice. The following table shows the differences in important 
data: 

Grams per Milligrams per ioo 

100 Grams of Vinegar: Grams of Vinegar: 

Phosphoric Phosphoric 
c c. -^-- acid Oxid in Oxid in 

10 Soluble Insoluble 

Acid. Solids. Ash. for ash. Ash. Ash. 

Maximum, 7.61 4.45 0.51 55.2 22.7 19.4 

Minimum, 3.24 2.00 0.31 28.4 13.6 4.2 

Average, 4.46 2.83 0.39 38.8 19. i 10. i 

Cider vinegar di- 
luted with 
water or spirit 
vinegar: 

Maximum, 4.83 3.41 0.53 29.6 15.2 20.2 

Minimum, 3.01 1.19 0.14 1.4 0.00 3.0 

Average, 4.00 2.03 0.24 18.4 5.2 5.7 

Sample from dried 
apples and glu- 
cose, 4.29 3.89 0.25 21.0 , 

Sample from cider 

and grape-juice, 4.54 2.77 0.30 34.0 

Smith finds that the ash of cider vinegar begins to melt and 
volatilize at a comparatively low temperature and gives to 
flame the potassium color unobscured by that of sodium. It 
is low in chlorids and sulfates and high in carbonates and phos- 
phates; about two-thirds of the phosphates are soluble in water. 
In the ash of other vinegars a much lower proportion of phos- 



u (c a 

iC IC II 



VINEGAR 285 

phates is soluble in water. The dilution of vinegar by natural 
water will be apt to reduce the soluble matter by the formation 
of calcium and magnesium phosphates. Manufacturers oc- 
casionally add potassium phosphate to diluted cider vinegars 
to correct deficiency. 

Cider vinegar is always levorotatory. With a 200 mm. tube 
the reading will range from o.i to 4.0 on the sugar scale. If 
the direct reading is right and the invert reading left, the sample 
probably contains added saccharine matter. If the both readings 
are right, glucose is present. If the reading is strongly left, un- 
fermented cider has probably been added to" increase the solids. 

U. S. Standard. 

Acetic acid not less than ..4 grams in 100 c.c. 

Apple solids '' " " ..1.6 

Apple ash '' " " ..0.25 

Water-soluble ash from 100 c.c. must require 30 c.c. -^ acid 
and contain not less than o.oio phosphoric oxid. 

Spirit Vinegar. — This is made by distilling a fermented mash 
of grain so as to obtain a very dilute alcohol, technically called 
"low wine," which is converted without rectification or con- 
centration into vinegar by the "quick" method above described. 
Spirit vinegar is often colored with caramel to simulate cider 
or wine vinegar. Pure spirit vinegar on evaporation leaves 
but a small amount of solids and a trace of ash. The following 
is a summary of the results obtained by A. W. Smith in the ex- 
amination of 65 samples of spirit vinegar: 

Average. 

Acetic acid, 2.87 to 5.99 3.84 

Total solids, , 0.14 " 0.78 0.38 

Ash, o.oi " 0.15 0.06 

The ash had a very slight alkalinity and only traces of phos- 
phates. 

Malt Vinegar. — This is characterized by a comparatively 



286 



FOOD ANALYSIS 



large amount of nitrogenous matter. The following table ex- 
hibits the usual composition as contrasted with vinegar prepared 
from glucose and sucrose. The water used in the preparation 
of the mash may have much influence on the composition of 
the ash. According to Sykes, various yeast-foods containing 
phosphates are often added to the wort with a view to stimulate 
the yeast and secure a higher production of alcohol. 



Analyst, 


A.W.Smith. 


Character of 


Malt, 


Vinegar. 


4 Samples. 


Per loo parts of vinegar : 


Percent. 


Acetic acid, .... 


4.01 to 5.90 


Total solids, . . . 


1.75 to 2.67 


Ash, 


0.20 to 0.2S 


" alkalinity, 


0.02 to 0.026 


Phosphoric oxid, . 


0.09 to 0.125 


Nitrogen, .... 


Not det. 


" Original solids," . 


7.76 to 11.06 



A. H. Alle.v. 



Malt. ^^'f^^^f^A'^^ FROM 

-4SAMPIFS H\DROL^ZtD BY c.-cab 

4 bAMPLES. SLLFURIC ACID. ^^'-^AR. 



^y^.T' Grams per 100 c.c. ^."l^P^'' 

100 c.c. *^ 100 c.c. 

4 86 to 6.61 5.5S 5.70 4.92 

2 31 to 3 96 2.9S 2.09 176 

034 to 055 0.30 0.43 0.278 

0.091 to o iiS o. 13 

0.057100093 0017 0.024 0.016 

0095 to 0120 0.104 0.062 0.016 

9.60 to 12 73 II 35 10.64 10.02 



4 



grams m 100 c.c. 



L' . S. Standard. 
Acetic acid not less than 
Solids '' " •• -.2 '' • 

Ash " •' '• -.0.2 " '' 

The water soluble ash from 100 c.c. must neutralize not less 



than 4 c.c. ^~ acid. 



10 



Malt vinegar is often made by acidifying dilute alcohol by 
the quick process and coloring the liquid by steeping in it a 
strongly scorched malt. This form contains less phosphates 
and solid matter than the older form of malt vinegar. Another 
method is the use of so-called ''malt acid," '' vinegar extract," 



VINEGAR 



287 



or ^'vinegar essence," obtained by acetifying dilute alcohol, 
neutralizing the liquid with lime and distilling the resulting 
calcium acetate with sulfuric acid by which a product contain- 
ing from 40 to 90 per cent, of acetic acid is obtained. The 
acetified alcohol, containing as much as 13 per cent, of acetic 
acid, is also sold under the name "Essig sprit" or "spirit vine- 
gar." The following analyses are due to Allen & Moor: 



Acetic acid, 

Total solids, 

Ash, 

Alkalinity of ash as potassium oxid, 

Phosphorus, 

Nitrogen, 

Sulfuric acid (free), 



" EssiG 
Sprit.' 



"Malt Acid." 



Grams per loo c.c. 



11.26 


88.02 


0.64 


2.77 


0.06 


0.15 


Trace 


. . 


0.014 


• • 



45-4 
12.14 

0.18 

0.017 
0.113 

0.074 



Commercial vinegars are made from these products by 
dilution with water and adding coloring and flavoring materials. 
According to Allen & Moor, it is the practice of some manu- 
facturers to distil a portion of the product, reserve the stronger 
portion of the distillate for sale as distilled vinegar, and add 
the weaker fractions to some of the undistilled article. Dis- 
tilled malt vinegar contains appreciable amounts of alcohol, 
ethyl acetate, furfural, and aldehyde, and has a highly character- 
istic taste and odor. 

^^ Original Solids.''^ — Hehner has called attention to the 
fact that additional information as to the nature of a vinegar 
may be obtained by calculating the weight of materials prior 
to fermentation. 90 parts of glucose should produce 60 parts 
of acetic acid ; therefore the amount of acetic acid in the sample, 



288 FOOD ANALYSIS 

multiplied by 1.5 and added to the solids, will give the figure 
termed by Hehner "original solids." The loss of acetic acid 
during fermentation may, however, be as much as 50 per cent., 
and the figure, therefore, will be only an approximation, but 
it is often instructive. The following table shows the method 
applied to the twenty-two samples of cider vinegar given on 
page 284. 

Milligrams of 
Milligrams of Phosphoric Oxid 
Solids X 1.5 Ash per 100 Grams per 100 Grams 
Acetic Acid. Original Solid. of O. S. 

Maximum, 14-38 6.09 3.77 

Minimum, 7.63 2.73 1.72 

Average, 9.65 4.1 1 3.10 

Analytic Methods. 

Acetic Acid. — This may be determined with sufficient accu- 
racy by diluting 5 c.c. of the vinegar with 50 c.c. of water and 
titrating with standard alkali, using phenolphthalein as in- 
dicator. 

Total Solids. — 5 c.c. of the vinegar are evaporated to con- 
stant weight in a platinum dish in the water-oven or on a water- 
bath. 

Ash. — A. W. Smith makes the following suggestions for 
its examination and determination: 10 grams of the sample 
should be evaporated and ashed by small portions (not more 
than 10 c.c.) at not above a low red heat. The residue is dis- 
solved and tested qualitatively by the flame-test and for chlorids 
and sulfates. Unless the latter are present in excess of the 
amount usually found in pure samples, they need not be de- 
termined quantitatively. For alkalinity of the ash and pro- 
portion of phosphates, 25 grams of the sample are dried and 
burned, the ash extracted repeatedly with hot water, pouring 
the solution through an ashless filter upon which the insoluble 
portion is collected. The filtrates are mixed and titrated with 
standard acid, methyl orange being generally used as indicator. 
Nitric acid is added to the liquid and the phosphates determined 



VINEGAR 289 

by the ammonium molybdate method. The filter is dried, 
burned, weighed, repeatedly extracted with hot dilute nitric 
acid, and the phosphate in the solution also determined. 

Nitrogen. — 50 c.c. are evaporated to small bulk and treated 
by the Kjeldahl- Gunning method. 

Mineral Acid. — If the ash be alkaline, no mineral acid can 
have been present except nitric acid; but if neutral, Ashby's 
test should be applied. A drop of solution of logwood ex- 
tract in water (0.5 gram to 100 c.c.) is dried on a porcelain 
plate, a drop of the vinegar added, and again dried. The 
residue from pure vinegar will be yellow, but will be red if min- 
eral acid be present. If the proportion of acid be small, the 
red color is destroyed by the addition of water, but is restored 
on evaporation, except in the case of nitric acid, which does 
not appear to be used for adulteration. 

The amount of free mineral acid is determined by Heh- 
ner's method as follows: 50 c.c. of the sample are mixed with 
a measured amount of decinormal alkali, preferably less than 
sufficient to neutralize all the acid, but rather more than suf- 
ficient to neutralize the mineral and fixed organic acids present. 
The mixture is evaporated to dryness, ashed at a low red heat, 
and titrated with standard acid. In the absence of mineral 
acid, the ash will have an alkalinity equal to the standard alkali 
added. Any deficiency in alkalinity will be due to the presence 
of mineral acid. 

Vinegar containing sulfuric acid usually leaves a charred 
residue on evaporation in the water-bath. For samples con- 
taining but little organic solids the test may be made applicable 
by adding a little sucrose. Sulfuric acid as distinguished from 
sulfates may be determined by Allen's method as follows: 100 
c.c. of the vinegar are evaporated to 10 c.c, and to the cold 
concentrated liquid 50 c.c. of alcohol are added. Sulfates are 
precipitated, but sulfuric acid remains in solution. The filtered 
liquid is diluted, the alcohol boiled off, and the sulfuric acid 
26 



290 FOOD ANALYSIS 

determined by precipitation with l^arium chlorid. In vinegar 
free from chlorids this process gives results in accordance with 
Hehner's process, but when chlorids are present the mineral 
acid found is deficient by the amount required to decompose 
the chlorids. This difficulty may be overcome by treating 
the sample with excess of solution of silver sulfate before evap- 
oration, by which any free hydrochloric acid will also be esti- 
mated as sulfuric acid. 

Caramel may be detected by the method given on page 130. 

Potassium acid tartrate, which occurs in true wine vinegar, 
may be detected by dissolving the solid residue in a little water, 
adding alcohol and stirring the mixture with a glass rod; the 
tartrate will be deposited in crystals along the lines touched ])\ 
the rods. 

Malic acid is alw^ays present in cider vinegar, and is indicated 
by a flocculent precipitate wdth lead acetate, w^hich settles 
quickly. Other vegetable acids may give such a precipitate. 
Leach ''^ distinguishes malic acid as follows: 

A few drops of a 10% solution of calcium chlorid are added to 
10 c.c. of vinegar and the liquid made slightly alkaline with 
ammonium hydroxid. Any precipitate is removed by filtration, 
30 c.c. of alcohol added to the filtrate and heated to boiling. 
Calcium malate will separate, which settles quickly, but pre- 
cipitates may also be formed in vinegar containing dextrin. 
The precipitate is collected on a filter, washed with a little alcohol, 
dissolved in strong nitric acid in a porcelain dish, and evaporated 
to dryness on the water-bath. The residue is boiled with 
sodium carbonate, filtered, the filtrate acidified with acetic 
acid, carbon dioxid expelled l^y boiling and calcium sulfate 
solution added. Calcium oxalate will be tlirown down if malic 
acid is present in the sample. The characteristic octahedral 
crystals can sometimes be recognized under high power. 

Poisonous metals may be encountered, especially in vinegar 
containing free mineral acid. Arsenic may be detected by 



SPICES 291 

Reinsch's test (p. 60). Lead, copper, tin, and zinc may be tested 
for directly in light-colored vinegars, but in most cases it will 
be necessary to examine the residue from a large amount of the 
sample in accordance with the methods given on page 581. 

SPICES 

Several processes applicable especially to, or modified for, 
the examination of spices require description. 

Moisture. — ^This determination cannot be made in the usual 
way on account of the loss of volatile oil. Richardson and Mc- 
Gill have devised methods for the purpose. 

Richardson's method is to dry 2 grams in an air-oven at 110° 
until the weight is constant, which generally requires twelve 
hours. The loss is moisture and volatile oil. The latter is 
determined from the loss in heating the total ether extract, as 
noted below, and, being deducted from the total loss on the oven- 
drying, leaves the moisture. Richardson found the data thus 
obtained to be satisfactory. 

McGill prefers to dry the weighed material in vacuum over 
pure, colorless, sulfuric acid. The moisture is first given off, 
and by watching the acid, the beginning of discoloration due 
to absorption of volatile oil and its carbonization by the acid 
will indicate the completion of the drying, and the sample can 
be weighed. About 24 hours are required for this. 

Ether -extract. — The ether-extract of spices, consisting of 
bodies volatile at widely different temperatures, must be dried 
in a definite manner to give comparable results. The following 
is the usual routine: When the extraction is completed, the 
ether is mostly distilled off (see page 42) and the remainder 
allowed to evaporate spontaneously at room-temperature. 
The container is placed in a desiccator over strong sulfuric 
acid for twelve hours, after which it is weighed; the weight is 
"total ether extract." The container is brought slowly up to 
100°, and then heated at 110° until wei^j^ht is constant. This 



292 FOOD ANALYSIS 

weight is "non-volatile ether extract." The difference between 
the two weights is volatile oil. 

Alcohol extract. — Winton, Ogden & Mitchell applied with 
advantage the method of extraction noted on page 42, using 2 
grams of the powdered material and 100 c.c. of alcohol. The 
liquid is filtered through a dry filter and a measured portion 
(50 c.c, equivalent to i gram of material is convenient) evapo- 
rated and the residue weighed. 

Tannins. — Determination of tannin is sometimes necessary. 
This is done most easily by Richardson's modification of the 
standard indigo method, which depends on the oxidation of 
the tannin by permanganate. ^° The solutions used are: 

Potassium permanganate. — 1.333 grams pure substance is 
dissolved in water and made up to 1000 c.c. The value of 
this in terms of oxalic acid should be determined as follows: 
10 c.c. of decinormal oxalic acid (6.3 grams of crytallized oxalic 
acid in 1000 c.c.) are diluted with water to 500 c.c, heated to 60°, 
20 c.c. of dilute sulfuric acid (i : 3) added and the permanganate 
solution added slowly w^ith constant stirring until the pink tint 
is no longer destroyed promptly. The value of the permanga- 
nate in terms of the indigotate solution should also be determined 
by titrating a mixture of 750 c.c of water and 20 c.c of in- 
digotate solution until a golden yellow liquid is produced. 

Indigo solution. — 6 grams of pure sodium sulfindigotate are 
dissolved in 50 c.c of water, by the aid of heat, cooled, 50 c.c 
of strong sulfuric acid added, and the solution made up to a 
liter. 

Two grams of the material are extracted for a considerable 
time with anhydrous ether and then boiled for two hours with 
300 c.c of water, cooled, made up to 500 c.c. and filtered. 
25 c.c of the filtrate are transferred to a 1200 c.c flask, 750 c.c. 
of water added and 20 c.c. of indigotate solution, and the mix- 
ture titrated with standard permanganate, until a golden 
yellow solution is produced. 



PEPPER 293 

The amount of permanganate required for the indigotate 
solution is deducted from the total permanganate used, and the 
value of the remainder is calculated to oxalic acid, i ex. of 
oxalic acid is equivalent to 0.0008 of absorbed oxygen or 0.00623 
of tannin, expressed as quercitannic acid. 

PEPPER 

Pepper is the fruit of the Piper nigrum L., of the order Pi- 
peracecB. Black pepper is the unripe fruit, dried in the sun; 
white pepper is obtained by soaking the ripe fruit in water and 
removing the husks by friction. 

Pepper contains alkaloid, piperin, an acrid resin, a volatile 
oil, starch, a small amount of nitrates, and the usual plant 
constituents. 

Piperin. — The proportion of this in pepper ranges between 
4 and 8 per cent. It forms colorless, four-sided, monoclinic 
prisms, melting at 128° and decomposing at a slightly higher 
temperature. It is insoluble in cold and but slightly soluble 
in hot water, dissolves in alcohol, forming a neutral solution 
of pungent taste, is freely soluble in chloroform, benzene, and 
petroleum spirit, but less so in ether. It is extracted even from 
acid solutions by chloroform. Boiled with strong alkali, it is 
converted into piperidin and a piperate. 

Piperidin is a colorless liquid with an odor recalling both 
ammonium hydroxid and pepper. It boils at 106°, is strongly 
basic, and may be estimated by titration with standard acid, 
using methyl-orange as indicator. Small proportions are 
found in pepper. According to Johnstone, black pepper con- 
tains from 0.39 to 0.77 per cent., and white pepper from 0.21 
to 0.42 per cent. 

The resin of pepper is dark green and has a hot pungent 
taste. It is soluble in alcohol, ether, and sodium hydroxid 
solution, and in water in the presence of the other constituents 
of pepper. 



2()4 



rOOD AXAIASIS 



The volalile oil of pc'|)i)cr is a tcrpene having a boiling-point 
of 167°-! 70°. Il lias the smell of ])cp})er, but not its pungency. 
It is usually present to the extent of about i per cent. 



am 



isf'- 




3 

Fig. 49. 
A, Starch granules (X 600); am, cell containing starch; p, parenchyma with 
resin; hj, bast fibers; hp, bast parenchyma; sp, spiral vessels; ep, epider- 
mis; ast, stony parenchyma; as and is, seed membrane in two layers; 
ist, inner stone-cell layer with horseshoe-shaped cells. The structures ist, 
as, and is are more characteristic, especially the two latter, consisting of a 
light and a dark layer. All (except A, as above) X 160. 



S larch. — Pepper-starch is in minute granules, not more than 
0.005 mm. in diameter, round or polygonal, and often in clusters. 
Under a high power they show a central nucleus or vesicle. 



PEPPER 295 

U. S. Standard, Black pepper. — 
Ash not more than . . 7.0 per cent. 

Ash insol. in hy- 
drochloric acid " " " . . 2.0 
Crude fiber '' " '' .-15.0 " 

Starch not less than -.25.0 

Non- volatile ether- 
extract '' " " .. 6.0 '' 
The non-volatile ether-extract must contain not less than 
3.25 per cent, of nitrogen. 

U. S. Standard, White pepper. — 
Ash not more than 

Ash insol. in hy- 
drochloric acid " " '' 
Crude fiber 

Starch not less thcin 

Non- volatile ether- 
extract " " " .. 6.0 " 
The non-volatile ether-extract must contain not less than 
4.0 per cent, of nitrogen. 

The microscopic appearance of ground pepper is shown in 
figure 48, from a drawing by Moeller.'*^ 

Adulteration oj Pepper. — The following are some of the 
adulterants which may be looked for in pepper: Pepper husks, 
long-pepper, wheat, buckwheat, cayenne pepper, mustard 
husks, ground olive stones (poivrette or pepperette), almond 
and cocoanut shells (often roasted or charred), Egyptian corn, 
spent ginger, and coriander seed. Of mineral additions, sand, 
clay, brick dust, chalk, barium sulfate, and lead chromate are 
known to have been used. 

In the examination of pepper, considerable reliance must 
be placed upon the microscopic characters. Numerous chem- 
ical examinations have been made, but the results in many 



.4.0 


per 


cent 


- 0-5 


a 


li 


- 5-0 


u 


a 


.50.0 


u 


ii 



296 FOOD ANALYSIS 

cases have been conflicting, and the uncertainty has been in- 
creased by the fact that, until recently, hardly any two workers 
have employed the same methods. 

Analytic Methods. Data. — These are directed to the de- 
termination of starch, ash, insoluble ash, non-volatile ether- 
extract, crude fiber and total nitrogen. The alcohol and water- 
extract have been shown to be valueless in this connection. 

Moisture. — This is determined as on page 291. 

Ether-extract. — This is termed non-volatile extract, because 
it is weighed after heating on the water-bath in order to drive 
out the solvent. It contains piperin, resin, and some volatile 
oil, and for the purpose of detecting adulteration is more 
convenient and satisfactor}- than the determination of piperin 
alone. If desired, the piperin may be determined as follows: 
The mixture of piperin and resin obtained by extraction is 
treated with sodium hydroxid, by which the resin is dissolved; 
the residue is dissolved in alcohol, the solution filtered, evapo- 
rated, and the residue (piperin) weighed. Another method is 
to mix a weighed portion of the powdered pepper with slaked 
lime and water, dry at 100°, and thoroughly extract with ether. 
The residue left on the evaporation of the ether is purified by 
solution in alcohol, filtration, and crA'stallization. 

The proportion of ether-extract is usually not less than 7 
per cent., but may fall below this figure even in pure peppers. 
(See standard, page 295.) 

Nitrogen. — Determination of total nitrogen by the Kjeldahl- 
Arnold method (see page 36) is now substituted for the piperin 
determination in the routine examination of pepper. 

Crude Fiber. — This should be determined on the ether- 
extracted material as described on page 38. Richardson's 
figures and those of Winton in the following table were ob- 
tained in this way. Those of Stokes were made without 
previous exhaustion with ether. Heisch reported "cellulose," 
but the method of determination is not stated. 



PEPPER 297 



Analyst, 


Richardson. 


WiNTON. 


Stokes. 


Heisch. 


Black pepper, . . 


. . -8.0 to II.O 


8.57 to 15.41 


21.0 to 26.3 


II. 5 to 27.8 


White pepper, . . 


...4.1 to 8.0 


3.32 to 4.16 


12.7 to 13.8 


34 to 6.7 


Long-pepper, . . 


. . . 


7-38 


20.0 to 22.3 


1. 14 to 12.9 


Pepper shells 


or 








dust, 


. . . 


22.8 






Olive stones,.. . 


. . . 




62.2 to 64.2 


61.9 to 68.8 



Ash. — In unadulterated black pepper the proportion of ash 
rarely exceeds 5 per cent.; over 7.0 per cent, may be taken as 
evidence of adulteration. The ash of white pepper should 
not exceed 4.0 per cent. If long-pepper be present, the ash 
is apt to be high, for the reason given below. Stock has pub- 
lished the following determinations in genuine peppers: 

Tellicherry. Siam. Lampong. Penang. 

Ash, 1.05 1.45 2.20 2.75 

Fiber, 4.86 4.43 4.90 5 .06 

Calc. carb. in pepper, 0-58 0.62 0.81 1.67 

" " "ash, 55-20 42.70 36.80 60.70 

Tellicherry Pepper. Unhulled. Hulled. 

Total ash, 4.02 i .64 

Fiber, 10.40 6.80 

Ratio of calcium (as carbonate) to ash, 27.30 62.00 

It is thus seen that calcium compounds are more abundant 
in pepper. Excess of hulls results in a lowering of this ratio, 
but the proportion may be altered in samples that have been 
bleached or faced with mineral matter. Stock considers that 
in pure pepper the proportion of calcium carbonate to total 
ash is never greater than 60 per cent. 

It is advisable to shake up a portion of the pepper-sample 
with chloroform in a tapped separator. The heavier mineral 
additions will sink, along with more or less husk, and may be 
removed by means of the tap and examined with the micro- 
scope and chemically. In this way it may be possible to dis- 
tinguish between added mineral matter and that naturally 
present. 

Winton has called attention to the fact that in the ether- 



298 FOOD ANALYSIS 

exlracl of pure ])i'[)|)er ihc pipcrin invariably crystallizes out 
Irom the resin on cooling, but that when pepper is adulterated 
with material containing fat or oil, the latter may conceal the 
crystals or prevent their formation. Absence of piperin crystals 
is regarded as positive evidence of adulteration. If the fat or 
oil introduced by the adulterant increases the weight of the 
extract to the amount which is found in pure pepper, a deter- 
mination of the nitrogen in the extract will often disclose the 
adulteration. 

Starch. — Many determinations have been made, but the 
methods used have been faulty and the indications often 
unsatisfactory. Hcisch boiled the pepper for three hours 
with 10 per cent, hydrochloric acid and measured the optic 
activity of the resulting liquid. The gum and other soluble 
matters were found to cause a rotation equivalent to about i 
per cent, of starch. Lenz extracted the pepper with water, 
boiled the residue with hydrochloric acid, and determined the 
reducing sugar. All the samples of pepper examined gave 
a reducing sugar equivalent of over 50 per cent., while the 
adulterants, except those containing starch, gave under 30 per 
cent. Rottger, however, found Lampong pepper to give a 
" reducing-sugar equivalent" of only 41.7 per cent. Richard- 
son found the starch in 5 samples of black pepper to vary be- 
tween 34 and 38 per cent, of the dry ash-free material. In two 
samples of white pepper the figures were about 40 and 43 per 
cent, respectively. 

Substances other than starch arc converted into sugar by 
the above processes. The U. S. standard for starch in pepper is 
based on the diastase method given on page 93. 

Ground olive-stones, termed "poivrette" and "peppcrette," 
have been much used to adulterate pepper. J. Campbell 
Brown, who first called attention to this use, has given the re- 
sults of analysis of samples: 



PEPPER 299 

Ash. Fiber. 

White pepperette, 1.33 48.48 

Black pepperette, 2.47 47-69 

Ground olive-stones, 1.61 45 -3^ 

Ground almond-shells, 2 .05 51 .68 

None of the samples contained starch. 

Poivrette is a pale buff or cream-colored powder, which can- 
not be distinguished from the materials of genuine pepper by 




Fig. 50. 

a, Cells associated with the vascular bundles, also some stone-cells; i, inner 
layer of hard cells, with endothelium en; p, cells from the fleshy portion 
of the fruit; ep, epidermis of the seed wall, with brown parenchyma showing 
through it; ea, exterior layer of the endosperm. Some spiral vessels are 
also shown. X 160. 

simple inspection. The particles are, however, tough and hard, 
and may be sometimes detected by crushing the sample between 
the teeth. Under the microscope the powder shows dense 
ligneous cells, sorne entire, with linear air-spaces, others torn 
and indistinct. Figure 50 shows some structures of olive seed 
and figure 51 some structures of nut-shcUs. Both are from 
Mocller's work.^^ 



300 



FOOD ANALYSIS 



By treatment with dilute sodium hydroxid solution and 
washing by decantation poivrette will appear yellow and pepper 
husk dark. Although poivrette contains no starch, it yields a 
reducing substance on boiling with hydrochloric acid. 

Bleached pepper husks are distinguished from poivrette by 
the microscopic appearance. An incomplete separation of 
poivrette may be effected by shaking the sample in a mixture 
of equal parts of glycerol and water, in which poivrette sinks 
more rapidly. 

Several color tests have been proposed. Gillet advises the 
use of a 7 per cent, alcoholic solution of iodin, which stains 

pepper brown and poivrette 
bright yellow. Chevreau uses a 
solution of anilin in three parts 
of acetic acid. Pure pepper is 
almost unaffected, but poivrette 
becomes bright yellow, and under 
the microscope the stone cells 
exhibit a pure gamboge yellow. 
Pabst uses a solution of di- 
methyl- 1-4-diamidobenzene, pre- 
pared as follows : i gram of com- 
mercial dimethvlanilin is mixed 
in a porcelain dish with 2 grams 
of strong pure hydrochloric acid, 10 grams of broken ice are 
added, and, little by little, wdth constant stirring, a solution of 0.7 
gram of sodium nitrate in 10 c.c. of water. After half an hour 3 
to 4 grams of hydrochloric acid and 2 grams of tin-foil are added. 
The reduction is allowed to go on for an hour, when the tin in 
solution is precipitated by means of zinc. The decanted and 
filtered liquid is treated with a slight excess of sodium carbonate 
and the precipitate thus produced redissolved by the addition 
of acetic acid, i gram of sodium acid sulfite is added and the 
liquid diluted to 200 c.c. In testing pepper, 2 c.c. of the solution 




Fig. 51. 

a, Exterior layer; m, intermediate 

layer; i, inner layer. 



PEPPER 301 

are placed in a shallow dish and a pinch of the pepper sprinkled 
into it. In a few minutes the particles of olive stones become 
a brilliant carmine, while the grains of pepper remain unaltered 
or become only faintly pink. If some water be now added, the 
heavy particles of olive stones fall to the bottom and are de- 
tected with ease. Ground nut-shells are colored in the same 
way. 

The phloroglucol-hydrochloric acid solution (page 26) pro- 
duces with olive stones and nut-shells a deep crimson stain 
which is very characteristic. The action is obtained promptly 
on moistening the sample with a few drops of the reagent. 
Under a magnifying power of about 200 diameters the stained 
stone-cells are clearly seen. 

Dhoura Corn. — This is a variety of sorghum, known in 
England as Turkish millet and in America as Egyptian corn. 
Brown called attention to its use in pepper, and gave the fol- 
lowing analyses and description. The two samples contained 
II per cent, of moisture; the figures are percentages of the dry 
material : 

Ash, 1 .3 1 1 .69 

Starch, 73-20 73-20 

Cellulose, 2.56 4.19 

Ether-extract, 11. 10 7.30 

Nitrogen, 1.82 1.78 

The material designated "cellulose" is probably crude fiber, 
obtained by using stronger solutions than directed in the A. O. 
A. C. method. The grain is roundish, oval, or somewhat 
flattened, 2 to 5 mm. in diameter. The body is white and con- 
sists mainly of roundish starch granules, the general characters 
of which are given on page 90. 

Coriander Seed. — Hanausek has called attention to the adul- 
teration of pepper with ground coriander seed. The following 
peculiarities were observed under the microscope : (a) bundles 
of corrugated bent fibrous cells; (b) coarse parenchyma over- 



302 FOOD ANALYSIS 

laid with narrow cells of a yellow color, with parallel walls; 
(c) colorless cellular parenchyma firm in the walls and in- 
closing numerous crystalline rosettes and granules. The last 
two peculiarities were recognized as characteristic of a fruit of 
the order Umhellijerce, the bundles of fibers, as well as the ab- 
sence of vitti€ (oil cavities), pointing to coriander. 

Cayenne pepper is often added to adulterated pepper to restore 
pungency. It may be detected by the characteristic irritating 
vapor produced on heating some of the separated red particles. 
An alcoholic or ethereal solution also gives off such vapors. 

LONG PEPPER 

Long pepper is the fruit of at least two species, formerly in- 
cluded under the genus Piper L. (Piperacece), now included 
under the genus Chavica Aliq. It consists of long, nearly 
cylindrical spikes, covered with closely packed coalesced fruit, 
which are picked unripe. The Chavica officinarum, from Java, 
consists of spikes about 4 to 6 cm. in length. The spikes of 
the Chavica Roxburgh ii are about half as long. The latter is 
the more common form. 

Long pepper usually contains a considerable proportion of 
extraneous matter (clay and soil) embedded in the crevices 
and irregularities of the fruit. The outer husk and central 
woody stem are not so readily removed as in the case of black 
pepper, so that the proportion of woody fiber is larger than 
in ground black pepper of the same shade, but not so high as in 
most husky black pepper. Long pepper contains less piperin 
than most black pepper, and has a disagreeable odor and flavor; 
in the ground state, it is not a recognized article of commerce. 
It is used whole in pickles and has been employed to adulterate 
ground black and white pepper. The following are some re- 
sults of analysis of long pepper: 



PEPPER 



303 



Total 
Ash. 


Ash Insol. 
Acid. 


Starch and 
IMatter Con- 
vertible 
INTO Sugar. 


Fiber. 


Ether- 
extract. 


Nitrogen. 


Analyst. 


8.91 


1.2 


44.04 


15-7 


5-5 




2.1 


Brown. 


8.98 


i.i 


49-34 


10.5 


4.9 




2.0 


(( 


9.61 


1-5 


44.61 


10.7 


8.6 




2-3 


(( 


8.10 






7.28 


.7.24 






Winter 



Winton's figures were obtained by the A. O. A. C. methods. 

According to Brown, long pepper may be detected in ground 
pepper by the following characters: The presence of any 
considerable quantity of long pepper will impart to the ground 
material its peculiar slaty color; but this is made much lighter 
by the practice of sifting out much of the darker or husky por- 
tions of the long pepper before mixing. Bleaching is also 
resorted to. The odor of the mixture when warmed is un- 
mistakable, even if the quantity is comparatively moderate. 
The ether- or alcohol- extract also, if the solvent has been evap- 
orated at a low temperature, yields the characteristic odor 
when warmed. 

Long pepper often introduces a considerable amount of 
mineral matter, especially sand and other material insoluble 
in acid. This fact is important in examining white peppers, in 
which the proportion of ash is low. Long pepper, even if the 
husk particles have been sifted out, Avill still introduce some 
sand, as well as spent bleach, if an attempt has been made to 
bleach it. 

The woody matter in ground long-pepper is always con- 
siderable. If the sample be spread out in a smooth thin layer 
on paper by means of an ivory paper-knife, pieces of fluffy 
woody fiber will be detected, especially if the smooth thin layer 
be tapped from below. These pieces come from the central 
part of the indurated catkin, which cannot be completely ground 
fine, and are very characteristic. 

Some of the starch granules of long pepper arc of larger 
size (0.005 "^rn-) than those of ordinary pepper, which are 
but slightly smaller than those of rice. 



304 FOOD ANATA'SIS 

According to Stokes, long pepper may be detected by placing 
a small portion on a microscope slide, adding a drop of glycerol, 
and examining under a power of about 50 diameters and crossed 
nicols. If ordinary pepper only be present, the Held will re- 
main dark, but long pepper presents a luminous white appear- 
ance. The same is true of particles of rice. By treating the 
fmely powdered material for 24 hours with chloral solution, it 
is rendered more transparent, and more satisfactory examina- 
tion may be made. Rimmington recommends shaking the 
material several times, first with alcohol and then with water 
in a test-tube, and allowing to subside. Several strata are 
usually formed, the uppermost of which should be removed by 
means of a pipet and examined with a power of 250 diameters. 
Every particle will be seen clear and well defined and foreign 
bodies easily recognized. 

CAYENNE PEPPER 

Cayenne pepper, the ground pods of several species of 
Capsicum, is a brick-red powder of intensely pungent taste and 
characteristic odor. When heated, an acrid, irritating vapor 
is given off, the production of which may be utilized as a test 
for the pepper, even on a minute quantity of the material. This 
action is due to a crystalline body that melts at 59° and 
volatilizes at 1 1 5°. It may be obtained by extracting the pepper 
with petroleum spirit, evaporating, and treating the dry extract 
with a dilute solution of potassium hydroxid. On saturating the 
liquid with carbon dioxid the substance is precipitated in small 
crystals, readily soluble in alcohol, ether, amyl alcohol, and fixed 
oils, but less so in petroleum spirit and carbon disulfid. It is 
usually more abundant in the pods than in the seeds, in which 
it exists dissolved in the fixed oil. It was discovered by Thresh, 
who found also a small quantity of an alkaloid resembling conin. 
The coloring-matter of cayenne pepper is but slightly soluble 
in alcohol, but dissolves readily in oils, carbon disulfid, petro- 



CAYENNE PEPPER 



305 



leum spirit, ether, and chloroform. The odor is due, at least 
in part, to the presence of a minute quantity of volatile oil. 

The following are some published analyses : 

Fruit of Capsicum annuum, grown in Hungary (Richard- 
son): 



Seed. 

Water at 100°, 8.12 

Albuminoids, 18.31 

Ether-extract, 28.54 

Nitrogen-free matter by difference,. . . .24.33 

Crude fiber, 17-5° 

Ash, 3.20 

Nitrogen, 2 .93 



Average of several analyses by Blyth : 

Water-extract, .32.10 

Alcohol-extract, 25 .79 

Benzene-extract, 20.00 

Ether-extract, io-73 

Nitrogen, 2.04 

Ash, 5.69 



Pod. 


Whole 
Fruit. 


14-75 
10.69 

5-48 

38-73 


11.94 
13.88 
15.26 
32-63 


23-73 
6.62 


21.09 
5.20 


1. 71 


2.22 



Two analyses by Richardson: 



Water. Ash. 

Zanzibar, 2.35 9.06 

Crosse and Blackwell,. .5.74 5.24 



Ether - 

EXTRACT. 

26.99 

17.90 



Fiber. 

16.88 

18.10 



Album- 
inoids. 

11.20 



Nitro- 
gen. 



1.79 



Adulteration. — The adulterant most commonly added to 
cayenne pepper is rice flour or similar material. Brick dust 
is also used. Allen found iron oxid, salt, and red lead. Starch- 
containing materials are readily detected by the microscope 
or by the iodin test. 

Results obtained at the Connecticut Agricultural Experiment 
Station indicate that pure cayenne pepper will contain not less 
than 16 per cent, of non-volatile ether-extract and between 4.5 
and 8 per cent, of ash. 
27 



3o6 rOOD ANALYSIS 

Hie (Iclcrminalions of extract, ash, nitrogen, and moisture 
are made by tlie methods elsewhere given. Barium com- 
pounds have been found in some samples, and it has been al- 
leged that they are normal, but this seems to be a mistake. 

An artificial red, containing barium, is sometimes used to 
color inferior samples, and possibly barium sulfate has been 
added as a make-weight. 
U. S. Standard. 

Non-volatile ether 

extract not less than . . 1 5.0 per cent. 

Ash not over .. 6.5 " *' 

Ash insol. in hydro- 
chloric acid " '' .. 0.5 " 

Crude fiber " '' ..28.0 '^ 

Starch " '' . . 1.5 " 



GINGER 

Ginger is the rhizome of the Zingiber zingiber (L) Karst. It 
exists in commerce in two forms, with the outer integument 
present, called "coated ginger," and removed by scraping, as in 
"uncoated" or "scraped ginger." Scraped ginger is some- 
times known as white ginger, and the same name is apphed 
to samples that have been bleached either with sulfurous acid 
or hyposulfites. It is also sometimes coated with lime or gyp- 
sum. Jamaica ginger is preferred in the United States. It 
forms a lighter colored powder than the other varieties. Gin- 
ger contains a volatile oil, a pungent resin, starch, gum, and the 
usual plant constituents. The volatile oil has the odor but 
not the pungency of ginger. 

Adulteration. — The most common adulteration of ginger is 
admixture with ginger that has been exhausted with dilute 
alcohol or water. P'or the detection of this, indications are 
furnished by the determination of the cold-water extract taken 



GINGER 307 

in conjunction with the soluble ash, as suggested by Allen & 
Moor. The following are some results obtained: 

Jamaica. 
a. b. Cochin. African. 

Moisture, 13.9 12.7 13.5 15.9 

Total ash, 3.9 3.2 3.8 3.6 

Soluble ash, 3.0 1.7 2.0 2.2 

Cold-water extract, 14.4 12.2 8.6 10.8 

Neither the soluble ash nor the cold-water extract alone 
will afford a means of deciding as to the presence of exhausted 
ginger, but by a combination of the two data it is possible 
to arrive at a positive conclusion. Thus, there is no diffi- 
culty in ascertaining the presence of the adulterant when it 
has been added in such quantities as to bring the soluble ash 
down to about i per cent, and the cold-water extract to less 
than 8 per cent. Stock recommends also a determination of 
the amount of potassium. The following are some results 
obtained by him: 

Soluble Ash. Potassium. 

Pure ground ginger (94 samples), 1.7 to 3.6 0.7 to 1.5 

Exhausted ginger, 0.2 to 1.6 0.016 to 0.7 

Turmeric, flour, ground husks and shells, seeds, or seed- 
cake are possible adulterants of ginger, and are best detected 
by means of the microscope. The form of the starch granules 
present will often furnish valuable indications. 
U. S. Standard. 

Starch not less than ..42.0 per cent. 

Crude fiber '' more '' ..8.0 " 

Calcium oxid...- '' " '' .. i.o '' '' 

Ash " '' " -.8.0 " " 

Ash insol. in hy- 
drochloric acid." " " .. 3.0 



(C II ^ ^ it n 



NUTMEG 

Nutmeg is the kernel of the seed of the Myristica jragrans 
Houttyn. The fruit is gathered and dried by slow heating, 



3o8 FOOD ANALYSIS 

after which the shell is removed and the inclosed nutmeg usually 
is coated by dipping in thick milk of lime. The nutmeg is 
oval or elliptical and about an inch in length. It has a strong, 
pleasant odor and warm, aromatic somewhat bitter taste. Nut- 
megs contain between 3 and 5 per cent, of volatile oil, con- 
siderable fat, starch, and proteids. The volatile oil is colorless 
or pale yellow and of specific gravity 0.92 to 0.95. It is freely 
soluble in alcohol and commences to boil at 160°. It is dex- 
trorotatory. According to Cloez, the most volatile portion is 
a terpene and is levorotatory. There is present also myristicol, 
dextrorotatory and boiling at 224°. On standing, myristic acid 
sometimes separates from the volatile oil. 
U. S. Standard. 

Ash not over .. 5.0 per cent. 

Ash insol. in hyclro- 

chloricacid " " .. 0.5 " 

Crude fiber '' '' ..lo.o " 

Non-volatile ether-ex- 
tract not less than 25.0 '' " 

Adulteration. — Nutmeg is little subject to adulteration, be- 
ing almost exclusively sold unground. Artificial nutmegs, 
containing some nutmeg oil, are said to have been prepared 
from starchy or mineral matter, but such imitation would readily 
be detected by the appearance of the cross-section compared 
with that of a genuine sample. 

For methods of analvsis, see under "Cloves." 



MACE 

Mace is the dried mantle or arillus of the nutmeg. It con- 
sists of smooth branching bands about 40 mm. long, 2 mm. 
at the base, and thinner above. It is brownish, has an odor 
like nutmeg, and a warm aromatic taste. ^lace contains a 



MACE 309 

volatile oil and a resin. It is stated that it contains no fat, 
but this does not accord with Spath's statement, given below. 
According to Fliickiger, there is also present an uncrystallizable 
sugar and a body that turns blue with iodin, and, after drying, 
reddish-violet. It appears to be intermediate between starch 
and mucilage. 
U. S. Standard. 

Ash not over 3.0 per cent. 

Ash insol. in h}^drochloric 

acid " " 0.5 " 

Crude fiber " '' lo.o '' 

Non- volatile ether extract . 20-30 '' " 

Adulteration. — In addition to the usual spice adulterants, 
mace is liable to contain Bombay mace, a variety which con- 
tains neither the fragrance nor the taste of true mace. Starch- 
containing adulterants may be detected by the fact that pure 
mace, boiled with water, yields an easily filtered solution, which 
is not blued by iodin. Determination of the am.ount of starch 
will furnish a rough indication of the proportion of adulterant 
present. False or Bombay mace may be distinguished by 
the altered proportion of volatile oil and of ether-extract. The 
following are some results obtained from true or Java mace 
compared with a sample of false mace : 

Fixed 
Lther- 
Water. Ash. \'ol. Oil. extract. Fiber. Nitrogen. 

True mace, 5.67 4.10 4.04 27.50 8.93 0.73 

" 4.86 2.65 8.66 29.08 4.48 0.98 

" " 10.47 2.20 8.68 23.33 6.88 0.81 

" " 18.21 1.62 3.37 21.90 3.70 

Bombay mace, . . 7.04 1.36 0.27 56.75 8.17 

E. Spath extracted a number of samples of mace with petro- 
leum spirit and determined the constants of the material ob- 
tained. The figures obtained from mace from Banda, Menado, 
Penang, Macassar, and Zanzibar closely agreed with each other: 



Melting- 






Zeiss 




point 


Saponi- 




Refracto- 


Index 


IN OPKN 


fication 


loniN 


METER 


OF 


Tube. 


Number. 


Number. 


AT 40'. 


Refraction. 


. . . .25-26 


169.9-173 


75.6-80.8 


76-85 


1. 480-1. 487 



IC FOOD ANALYSIS 

Meissl 
Number 
(Handa 
Mack). 

4.1-4.2 

Bombay mace, .31-31.5 189.4-191.4 50.4-53.5 48-49 i. 463-1.464 i.o-i.i 

F'rom macc 

scales, /. c, 

"the covering 

inside the 

seed-mantle, "28.5-29 148. 2-148. 8 71.3-73.4 

According to Konig, a sample containing less than 3 per cent, 
of volatile oil or more than 35 per cent, of extract on the dry sub- 
stance cannot be regarded as true mace. False mace is also 
distinguished by the presence of a peculiar coloring-matter, 
analogous to that of turmeric, rather freely soluble in alcohol 
and but slightly soluble in ether. The large oil cells of the 
false mace contain, according to Hanausek, a resinous body 
with which alcohol produces a yellow or greenish-yellow solu- 
tion, turned orange-red by alkalies. If 10 to 20 c.c. of alcohol 
are shaken with 2 or 3 grams of powdered mace for a few min- 
utes and the liquid filtered, the filtrate, but not the filter-paper, 
becomes colored. In the case of false mace the strongly colored 
filtrate dyes the paper a fixed yellow. If the filter is dried, 
freed from the attached powder, and touched with a weak al- 
kaline solution, the presence of turmeric is indicated by a brown, 
and of false mace by a blood-red, color. If the alkali be re- 
moved by washing the filter with water, a trace of acid will be 
sufficient to bring back the yellow. Hafelman suggests de- 
composing an alcoholic extract with lead acetate. Genuine 
mace gives a milk-white turbidity; false mace, even when 
mixed with a large proportion of true mace, gives a red floccu- 
lent precipitate. Turmeric produces a somewhat similar color. 
If a strip of filter-paper be dipped into the alcoholic extract, 
gently dried, and then drawn through a cold saturated solu- 
tion of boric acid in water, the presence of a very small 
quantity of turmeric will be indicated by an orange or red- 



ALLSPICE 311 

brown tin. With false mace, on the other hand, the yellow 
color of the paper will remain unchanged. 

Soltsien has called attention to the difference between 
Bombay and Banda mace as regards the quantity of matter 
extracted by ether after removal of the fat-like bodies by 
petroleum spirit, and suggests that advantage be taken of the 
fact in order to distinguish between the two. The difference 
is very considerable, the quantity being about ten times as 
great with Bombay mace as with true mace. Soltsien has 
never found more than 4.8 per cent, of matter extracted by 
ether in a pure Banda mace, and suggested 5.5 per cent, as a 
maximum. 

The examination is carried out as follows: 10 grams of 
powdered mace are exhausted with boiling petroleum spirit 
in a flask provided with a well-cooled inverted condenser. On 
cooling, an oily portion may separate ; this belongs prop- 
erly to the extractive matter soluble in ether. The petroleum 
spirit is poured off, the separated oily portion in the flask 
washed with petroleum spirit, dissolved in absolute ether, 
and then a second extraction is made with boiling ether. In 
the ether-extract there is also a tendency of a portion to sep- 
arate out. The extract is poured off, the separated matter 
washed with ether, and the washing added to the extract, which 
is then filtered, evaporated, and dried in the water-bath, the 
residue being weighed. 

ALLSPICE 

Allspice or pimento is the dried fruit of Pimenta pimenia 
(L) Karst. It is nearly globular, 6 mm. or less in diameter. 
Allspice contains volatile oil, fixed oil, resin, tannin, starch, 
sugar, and mucilage. The volatile oil is similar in composition 
and general properties to oil of cloves. The yield is usually 
between 3 and 4 per cent. 

Adulteration. — On account of its cheapness, allspice is less 



312 FOOD ANALYSIS 

subject to adulteration than other spices. In addition to the 
usual spice admixtures, clove stems and the lowest grades of 
cloves are sometimes added. These latter may be detected 
by the microscope, and also, in some cases, by the greatly in- 
creased proportion of volatile oil. 
U. S. Standard. 
Quercitannic acid (tannin), not less than 8.0 per cent. 

Total ash, not more than 6.0 " " 

Ash insol. in hydrochloric acid, not over 0.5 " '' 

Crude fiber, not over 25.0 " '' 

A sample of pure, whole Jamaica allspice examined by 
Winton gave the following results: 

Volatile oil, 352; non-volatile ether-extract, 6.48; ash, 4.57 

12 samples of commercial ground allspice, in which no adul- 
terant could be detected, gave results as follows: 

Volatile oil, 2 .05 to 2 .84 

Non-volatile ether-extract, 3.98 to 5.62 

Ash, 4.62 to 5.50 

Analytic Methods. — IMoisture, volatile oil, tannin, and fixed 
ether-extract arc determined as described on pages 291 to 

293- 

CINNAMON 

Cinnamon is the inner bark of several species of Cinna mo- 
mum. Commercial cinnamon may be divided into three classes 
as follows: 

1. True or Ceylon cinnamon. This is the finest quality, 
and is the one which is official in most pharmacopeias. It is 
rarely found in the grocery trade, and is used as a drug. In 
its preparation for the market it is deprived entirely of the outer 
coating and inner cortical layers, and forms long strips, usually 
not above the thickness of stout writing-paper. 

2. Common or Chinese cinnamon, known as cinnamon 



CINNAMON 



313 



cassia or cassia bark. It is thicker than true cinnamon and 
generally covered with patches of cork. It has a less dehcate 
and more astringent taste than true cinnamon. The variety 
of cassia known as Saigon cassia is said to have greater strength 
than true cinnamon. 

3. Malabar cinnamon, including inferior quahties from the 
East Indies and adjacent mainlands, from which the common 
ground cinnamon of the retail trade is usually prepared. 

Microscopically, true cinnamon may be distinguished from 
cassia by the presence in the former of long cells of woody fiber, 
which are especially well shown under polarized light. 

The following are some analyses of pure samples : 



Analyst. 




Water 


Ethe- 
real 
Oil. 


Fixed 
Ether 

Ex- 
tract. 


Crude 
Fiber. 


Nitro- 
gen. 


Ash. 


Konig and Krauch 


Ceylon cinna- 
mon, , . . 


12.44 




1-45 


■ 
35-46 


0.64 


3.28 


C. Richardson 


Ceylon cinna- 
















mon, . . . 


10.00 


3-H 


3?,0 


16.18 


0.61 


3-70 


tt 


Ceylon cinna- 
mon, . . . 


5-40 


1.05 


1.66 


33-08 


0.48 


4-55 


(( 


Ceylon cinna- 
mon, . . . 


7-93 


0.82 


1.58 


25.63 


0.62 


3-40 


Konig and Krauch 


Cassia bark, . 


1395 




3.26 


17.72 


0.62 


2.22 


<; < ( 


(( << 


14.44 




1.24 


17.76 


0.46 


1.96 


C. Richardson 


<< <( 


9.42 


58 


1.40 


17-73 


0.45 


2-35 


(( 


<( i( 


11.04 


1. 21 


1.86 


'5-45 


0.72 


2.48 


(( 


<( li 


17-45 


0-55 


0.74 


14-33 


0.64 


5-25 



The ash of pure cinnamon is usually white, while that of 
cassia is often brown, due to the larger proportion of man- 
ganese oxid. 

The items volatile oil, alcohol-extract, insoluble ash, and 
28 



314 FOOD ANALYSIS 

nitrogen appear lo furnish the most assistance in determining 
the proportion of admixture. 

The chemical composition of cinnamon and cassia is in the 
main the same. Each contains a volatile oil, tannin, sugar, 
mannite, starch, and mucilage. The essential oil of Ceylon 
cinnamon is pale yellow or reddish, becoming darker and 
thicker on exposure, and depositing crystals of cinnamic acid. 
It has a strong odor of cinnamon and a sweet, warm, aromatic 
taste. The specific gravity of the fresh oil is 1.035. In some 
cases it is slightly levorotatory. The essential oil of cassia 
has similar properties, but its color is more brownish, taste 
less sweet, odor less dehcate, specific gravity greater f 1.05 5 to 
1.065), ^^d ^s sometimes slightly dextrorotatory. Both oils 
contain variable quantities of hydrocarbons, but consist chiefly 
of cinnamic aldehyde, and, when old, contain resin and cinna- 
mic acid. 

Adulteration. — The chief adulteration consists in the substi- 
tution of the inferior cassia for the true cinnamon. As noted 
above, the true cinnamon is now only obtained as a drug. They 
may be distinguished by the difference in their microscopic 
characters. Aside from this, the most important adulteration 
consists in the partial abstraction of the ethereal oil, on which 
the value of the spice depends, either by alcohol or by distilla- 
tion with water. Sophistication of this kind is difficult to de- 
tect, by reason of the variations of the original bark in com- 
position. The lower grades of ground cinnamon are also adul- 
terated with barks of allied species, refuse found in the bundles 
of cinnamon as imported, mahogany and other woods, flours 
of various kinds, oil-cake, and similar materials. These are 
often readily detected by the microscope. 

U. S. Standard for ground cinnamon or ground cassia. 

Ash, not over 8.0 per cent. 

Sand/' " 2.0 " " 



CLOVES 315 

In Austria, Bavaria, and Switzerland, cinnamon or cassia 
containing more than 5 per cent, of ash or i per cent, of sand 
is held to be adulterated. 



CLOVES 

Cloves are the unexpanded flowers of the Eugenia aromatica 
O. Kuntze. They consist of a dark brown, cylindrical calyx, 
3 to 4 mm. thick, bearing a several- celled ovary and a globular 
head of four petals. Many oil glands are under the epidermis. 

Cloves contain a volatile oil, resin, tannin, and gum, but no 
starch. The volatile oil is thicker than most essential oils and 
becomes still thicker and darker with age. It has the odor of 
cloves and a burning aromatic taste. Its specific gravity is 
from 1034 to 1056; it boils at 240°. The oil obtained from 
clove stalks has a specific gravity of 1.009. Oil of cloves dis- 
solves freely in alcohol. Strong solution of potassium hydroxid 
converts it into a crystalline mass of potassium eugenate. It 
is sometimes slightly dextrorotatory. It consists principally of 
a hydrocarbon and eugenol (eugenic acid). On distilling a 
mixture of cloves and potassium hydroxid solution, the hydro- 
carbon is obtained as an oil of specific gravity 0.918, boiling at 
251°. By decomposing potassium eugenate with sulfuric acid 
and distilling, eugenic acid is obtained as a colorless oil of spe- 
cific gravity from 1076 to 1078, boiling at 247.5°. Caryophyl- 
lin and a salicylic ester have also been found. 

Adulterations. — In addition to the adulterants usually em- 
ployed for ground spices, clove stems and the fruit of the clove, 
the so-called ''mother-cloves," may be added. Clove stems 
may be detected by the microscope by the presence of numerous 
stone cells, bast fibers, and scaliform ducts. The form of the 
stone cells varies greatly; the walls are thick and the interior 
cavity may be simple or ramifying. The bast fibers are usually 
long, spindle-shaped, and thick. The scahform ducts, together 



3i6 



FOOD ANALYSIS 



with the stone cells, are the best evidence of the presence of 
clove stems. In mother-cloves, the stone cells are very thick- 
walled and ha\e a nodulated exterior, which enables them to 
be distinguished easily. The seeds contain starch and raph- 
ides. The starch granules resemble those of some kinds of 
arrowroot; they are principally pear-shaped, or, rather, slender 
and slightly curved, generally single, and show a well-marked 
cross under polarized light. There is a small hilum at the 
broad end. The resemblance to arrowroot starch is not likely 
to cause confusion, as the latter is too costly for use as an adul- 
terant. 

Cloves are also adulterated by the addition of samples from 
which a portion of the essential oil has been removed. This 
is usually difficult of detection on account of the great varia- 
tion in the amount of oil found in pure samples. 



ANALYSES OF CLOVES AND STEMS 



Water, 

Ash, 

Volatile Oil, . . . 
Fixed ether-residue. 
Crude fiber, . . . 
Nitrogen, .... 
Analyst, 



Whole Cloves. 



16.39 

4-«4 
16.98 

6.20 
10.56 

0.95 
Laube and 
Allendorf 



2.90 to 10.67 
525 " 1305 



10.23 '• 
7.12 " 
6.18" 
0.76 " 
Richardson, 
7 samples 



18.89 
10.24 

9-75 
1. 12 



9 to 21 



Dietsch 



Stems. 



10.18 

6.96 

4.40 

403 
1358 

0.92 
Richardson 



In 20 samples, either known to be pure or in which no adul- 
teration could be detected by the microscope, Winton found 
the following range in composition: 

Per Cp:nt. 

Volatile oil, 10.01 to 18.32 

Fixed ether-extract, 4.90 " 6.20 

Ash, 6.50 " 7.95 



MUSTARD 317 

U. S. Standard. 

Volatile ether-extract, not less than 10. o per cent. 

Quercitannic acid (tannin), not less than. .12.0 " " 

Total ash, not more than 8.0 " 

Ash insoluble in hydrochloric acid, not more 

than 0.5 " " 

Crude fiber not more than 10. o " " 

Analytic Methods. — Moisture, volatile oil, tannin and 
ether-extract are determined by the methods given on pages 
291 to 293. Crude fiber is determined on the residue from the 
ether-extract. 



MUSTARD 

Mustard is prepared from the seeds of the Brassica nigra 
Koch (black mustard) and B. alba Hkr. f. (white mustard). 
Commercial mustard may be a mixture of the two forms. The 
seeds are finely powdered and passed through a sieve in order 
to remove husks. Both forms contain a fixed oil in fairly con- 
stant proportion, albuminous matter, gum, sinapin thiocyanate, 
and an enzym, myrosin, but no starch. White mustard con- 
tains also the glucosid, sinalbin; and black mustard the glu- 
cosid, potassium myronate. These glucosids are decomposed 
by the enzym, on addition of water. 

Allyl isothiocyanate, volatile oil of mustard, is a colorless 

_o 

liquid, specific gravity —5^ 1.018, boiling at 148° -150°, and vola- 
tile in a current of steam. It has a strong mustard-like odor and 
the vapor excites a flow of tears. It is slightly soluble in water 
and much more so in alcohol, ether, petroleum spirit, and carbon 
disulfid. It is a powerful rubefacient and vesicant. 

Acrinyl isothiocyanate is a yellow liquid of pungent burning 
taste. It is a less powerful vesicant than the oil from black 
mustard and is but slightly volatile in steam. It is insokiblc 
in water, but soluble in alcohol and ether. 



31 8 FOOD ANALYSIS 

M^rosin is coagulated by heat, so that if mustard be intro- 
duced into boiHng water, no volatile oil is produced. 

The fixed oil of mustard has the following physical and 

I "° 
chemical constants: Sp. gr., ^^o, 0.914 to 0.920; saponifica- 
tion value, 170 to 175; iodin value, 92 to 106. About 35 per 
cent, is usually present. Commercial samples of good quality 
may contain much less, a portion having been expressed in 
the manufacture of the mustard flour. 

The following are some results of examination of pure samples : 
Mean of three closely concordant analyses of white mustard 
bv Leeds and Everhart : 

Water, 6.83 per cent. 

Potassium m}Tonate, 0.64. " 

Sinapin thiocyanate, 11. 12 " 

Myrosin and albumin, 28.48 " 

Fixed oil, 29.21 " 

Ash, 3.75 " 

Variations in composition of ground mustard seeds, accord- 
ing to figures published by A. O. A. C. : 

Per Cent. 

^Moisture, 3 to 8 

Ash, 4 to 7 

Ether-extract, 31 to 37 

Fiber, 4 to 6.5 

Aqueous extract, 30 to 38 

Sulfur, I to 1.6 

When prepared from partially expressed seeds, the mustard 
will contain less oil (ether-extract) and a correspondingly larger 
proportion of the other ingredients. 

Adulteration. — The most common adulterant for mustard is 
rice flour or wheat flour. These are readily detected by the 
microscope and by the presence of starch. This may also be 
present as a constituent of turmeric, added to color pale samples. 
Starch may be detected by boiling a portion of the sample with 
water, filtering, and adding iodin to the filtrate. It is determined 
as on page 93. The proportion of starch in wheat flour is about 



MUSTARD 319 

72 per cent. Allen suggests the determination of the amount 
of fixed oil, which is usually about 35 per cent., and calculat- 
ing from its deficiency the proportion of diluent present. In 
view of the practice of some manufacturers of pressing the 
seed, such a method is no longer reliable, but may often be of 
value as corroborative evidence. 

Of mineral additions, calcium sulfate, chalk, and lead chro- 
mate have been employed. These are detected in the ash. 

Leach^^ has made special investigations into the characters 
of commercial mustards. 

Volatile oil. For the determination of this, which, as 
noted above, does not pre-exist in the seed. Leach recommends 
Roeser's method: 

5 grams of the sample are mixed with 60 c.c. of water 
and 15 c.c. of 60 per cent, alcohol, allowed to stand for two 
hours, and then distilled into a flask containing 10 c.c. of 
ammonium hydroxid, until 50 c.c. of the original liquid has 

passed over. The distillate is mixed with 10 c.c. of -^ 
silver nitrate, allowed to stand 24 hours, made up to 100 c.c, 
filtered, 50 c.c. of the filtrate mixed with 5 c.c. of -^ potas- 
sium cyanid solution, and the excess of cyanid titrated with 
-^ silver nitrate, using a 5 per cent, solution of potassium 
iodid as indicator. The number of c.c. of --— silver nitrate 
taken up by the oil, multiplied by 0.6274, will give the per- 
centage of volatile oil of mustard. 

Although mustard contains no starch, Leach points out 
that som^e of the tissue of the seed will produce a reducing 
sugar even bV the diastase method, so that error may be made 
in this respect. It must also be borne in mind that mustard 
may be gathered from fields in which starch-bearing weeds 
are growing, and thus admixture with starch occur. Leach 
found starch grains due to this cause abundantly in a Dakota 
mustard-flour. Such admixture can be easily detected by 



320 FOOD ANALYSIS 

the microscope, using the potassium iodid-iodin solution, 
page 26. Pure mustard flour will not give blue granules. 
U. S. Standard. 
Starch (calculated from the reducing sugar 

obtained by diastase method), not over 2.5 per cent. 

Total ash, not over 8.0 " '' 

Coloring-matters are frequently added, the most common 
being turmeric, Martius' yellow, and naphthol yellow S. Coal- 
tar colors may be detected by methods given on pages 64- 
75; turmeric, by the test given under "Mace" or by the 
principle of the test for boric acid, page 82. 

FLAVORING EXTRACTS 

Vanilla Extract. — Vanilla is the pod of Vanilla planijolia, 
an epiphytic orchid of tropical regions. Its flavor depends on 
an aldehydic benzene derivative called vanillin. The amount 
present differs much in different samples and bears no constant 
relation to the source or price of the pod. 

The most expensive grades of extract are made by macera- 
ting vanilla beans in 50 per cent, alcohol. The cheaper grades 
contain cumarin (from Tonka bean), artificial vanillin, some 
glycerol, and caramel or coal-tar colors. The cumarin may be 
either added as such or obtained by macerating tonka beans 
in the solvent. In cheap extracts a very dilute alcohol is used 
and the solvent action often aided by some alkaline substance, 
generally acid potassium carbonate. The following is a pub- 
lished formula for a very cheap imitation extract: 

Vanillin, i gram . 

Cumarin, i gram. 

Alcohol, 125 c.c. 

Glycerol, 65 c.c. 

Water, i liter. 

Caramel to color. 

Commercial vanilla extracts have been examined bv Hess.^^ 



FLAVORING EXTRACTS 32 1 

He gives the following test as a critical one: A portion of the 
sample should be mixed with a few drops of lead acetate solu- 
tion ; if a bulky fiocculent precipitate does not form, the extract 
is not of high quality. The process given by Hess may then 
be applied to establish its general character: 

5 c.c. of the extract are diluted slowly with 10 c.c. of water 
and the mixture shaken. A fiocculent reddish-brown precipitate 
shows that no alkali has been added. A milky solution in- 
dicates a foreign resin. Hydrochloric acid is added drop by 
drop to a portion of the diluted liquid; only a slight turbidity 
should result. If the turbidity is considerable and the color 
fades, alkali has been employed in making the extract. 

25 c.c. of the sample are concentrated on a water-bath until 
the alcohol is removed and made up to the original volume 
with water. The vanilla resin will appear as an amorphous, 
fiocculent, reddish-brown mass if alkali be present. The cold 
solution is acidified with hydrochloric acid, when the whole of 
the resin will separate, leaving the liquid nearly colorless. 
After standing several hours the residue should be collected on 
a filter, washed with water, and the filtrate and precipitate 
further tested. 

A piece of the filter with resin attached is placed in sodium 
hydroxid solution. A deep red solution should be formed. 
A solution of the portion of the precipitate in alcohol should 
not give any marked reaction with ferric chlorid or hydrochloric 
acid. 

A portion of the filtrate is concentrated at a low temperature 
until its color approximates that of the original sample, a few 
drops of strong hydrochloric acid are added, and gently heated. 
Caramel will produce a yellowish-red fiocculent precipitate. 
The liquid is allowed to cool, filtered, and the precipitate washed 
with water; if from caramel, the precipitate will be insoluble in 
water, alcohol, and ether, soluble in sodium hydroxid, glacial 
acetic acid, and dilute alcohol. 



^22 FOOD ANALYSIS 

A small portion of the filtrate is made alkaline with am- 
monium hydroxid; natural color is much deepened. Zinc 
dust is added, and the liquid warmed gently. The color should 
return to about the tint it possessed before the ammonium hy- 
droxid was added, but azo-colors will be completely bleached. 
If the latter effect occurs, some of the liquid should be mixed 
with hydrogen dioxid, when the color will return. 

The caramel test described on page 124 will probably be of 
ser\'ice in these examinations. 

Determination oj Vanillin. — A rapid valuation of vanilla ex- 
tracts may be made by the following colorimetric method.^ 
Several reagents are required. 

Lead hydroxid. — 200 grams of lead acetate are dissolved in 
about 800 c.c. of water, the liquid filtered, a solution of potas- 
sium hydroxid added in slight excess, and the precipitate washed 
several times until free from alkali. It should be kept mLxed 
with excess of water in a well- stoppered bottle, the mLxture be- 
ing shaken when used. 

Bromin water. — Saturated solution of bromin in water. 

Ferrous suljate. — Freshly-prepared. 10 per cent, solution in 
water. 

Standard Vaniilin. — Freshly-prepared solution 0.050 gram' 
vanillin in 2^ c.c. of alcohol, made up to 100 c.c. with water. 
I c.c. contains 0.0005 vaniUin. 

2 c.c. of the vanilla extract are mLxed in a test-tube with 
sufficient lead hydroxid to decolorize, the mLxture transferred 
to a filter, washed and the filtrate and washings mLxed. A 
little bromin-water is added and then the ferrous sulfate solu- 
tion until the bluish-green does not increase. The color thus 
obtained is compared with similar volumes of liquid containing 
known amounts of vanillin treated in the same way. These 
comparison solutions are made by diluting with water, different 
measures of the standard vanillin solution, and adding the 
reagents. Thus i c.c. of the solution contains 0.00005 vanillin. 



FLAVORING EXTRACTS 323 

Dilute solutions may be made with quantities of the standard 
ranging from 0.5 c.c. to 5 c.c, but after a little practice in this 
class of testing, it becomes easy to approximate the color, and 
only a few comparison dilutions need be made. The liquids 
compared should be made up to the same volume and examined 
in colorless tubes of sensibly identical size and shape. The so- 
called '' Nessler tubes " for water analysis are preferable. These 
are marked at 50 c.c, a convenient volume. 

For the exact determination of vanillin (and cumarin) the 
following process is recommended. It is Hess & Prescott's '""^ 
method modified by Winton''^: 

25 grams of extract are evaporated on the water-bath at a 
temperature not exceeding 80° — with occasional addition of water 
to maintain the volume — until all alcohol is removed. Lead 
acetate solution is added drop by drop until no further pre- 
cipitate forms, the liquid is stirred to promote flocculation, 
filtered through a wet filter, and the precipitate washed three 
times with hot water. The mixed filtrates are allowed to cool, 
and extracted four times with ether, using about 15 c.c. each 
time. The completion of the extraction may be determined 
by evaporating a few drops of the ether on a watch glass; no 
appreciable residue should be left. The combined ether ex- 
tracts, which contain all of the vanillin and cumarin, are shaken 
five times with 2 per cent, solution of ammonium hydroxid, using 
10 c.c. for the first time and 5 c.c. for the subsequent ones. The 
whole of the vanillin will pass into the ammonium hydroxid. 

The ether is washed into a weighed dish and allowed to evap- 
orate at room temperature, then dried in a desiccator and the 
weight of residue (cumarin) taken. 

The vanillin solution is rendered slightly acid by hydro- 
chloric acid, shaken with four portions of ether as at first, the 
portions mixed, evaporated at room temperature, dried ()\-er 
sulfuric acid and weighed. 

The vanillin and cumarin thus obtained may not be pure, 



324 FOOD ANALYSIS 

and if very accurate determination is needed, each residue 
should be separately dissolved in petroleum spirit, boiling at 
about 35° (commonly sold as "legroin"), using small portions 
at a time until all the soluble material is dissolved. The un- 
dissolved matter is dried for a few minutes at ioo°, weighed 
and deducted from the first weight. The ligroin solution of 
vanillin evaporated at room temperature and dried in a desic- 
cator should leave a residue melting at 8o°-8i° and having the 
odor of vanillin. Synthetic and natural vanillin are identical. 

The cumarin solution evaporated at room temperature should 
leave a residue melting at 67° and having the odor of cumarin. 

Leach^® states that vanillin and cumarin, crystallized from 
ether, show difTerences wdth crossed nicols, vanillin giving, even 
without selenitc, marked color, but cumarin none. Vanillin 
gives a more marked color with sodium nitrite and sulfanilic 
acid, but the reaction is not characteristic. 

Lemon extract is a solution of lemon oil and the soluble 
matters of lemon peel in alcohol. The lemon peel is principally 
for coloring purposes. Commercial lemon extracts depart 
much from this standard. The lemon oil is often in small 
amount, even absent; other oils are substituted and coloring 
matters other than lemon peel. ^Methyl alcohol may be present. 
The Pharmacopeia standard is 5.0 per cent, of lemon oil, but 
it must be borne in mind that this is a drug- not a food- 
standard. Some commercial extracts will exceed this. The 
following formula for a cheap lemon-extract is quoted from a 
trade circular: 

Lemon oil, i gram 

Lemon-grass oil, o i c.c. 

Citric acid, 0.5 c.c. 

Alcohol, 16.0 c.c. 

Water, i lo.o c.c. 

Turmeric tincture to color. 

Lemon Oil. — This is principally the dextrorotatory form of 



FLAVORING EXTRACTS 325 

a terpene hydrocarbon, limonene, with an aldehyde, citral, 
and smaller amounts of analogous bodies. Lemon oil is in- 
soluble in weak alcohol. 

Oil of citronella and oil of lemon-grass are volatile oils of the 
same general character as lemon oil and often substituted 
for it. 

The examination of lemon extract is directed principally to 
the determination of the amount of lemon oil, and the detec- 
tion of added colors and methyl alcohol. The methods have 
been carefully investigated by Mitchell," and his results are here 
summarized. 

Lemon oil may be detected by diluting the extract with 
considerable water. If no turbidity results, the oil is not present 
in appreciable amount. In the absence of other optically 
active bodies the amount may be determined by the polarimeter, 
using a 200 mm. tube. The sugar-scale reading divided by 
3.2 will give the percentage of oil. Sucrose may, however, 
be present. If this is the case, 10 c.c. of the sample must be 
evaporated to dryness, washed several times with portions of 
5 c.c. of ether, the residue dried and weighed, and for each 
0.1 of this 0.38 is deducted from the calculated percentage of 
oil. 

Added colors. — The detection of these will be along the lines 
indicated on pages 64 to 75. The addition of hydrochloric acid 
may give useful indications. Turmeric, naphthol yellow S, nat- 
ural lemon color and fustic yellow are not affected; azo- colors 
are turned pink, dinitrocresols and naphthol yellow (Mar- 
tius' yellow) are bleached. 

Sucrose, Invert Sugar and Glycerol will be indicated in the 
residue on evaporation. Capsicum will be detected in this by 
taste. Invert sugar is, of course, also indicated by the levoro- 
tatory reading. 

For the detection of citric and tartaric acids see under "Fruit 
Sirups." 



326 FOOD ANALYSIS 

A special lest for citral, citronellal and limonene is given by 
Burgess^*: 10 grams of mercuric sulfate are dissolved in a mix- 
ture of 20 c.c. sulfuric acid and 85 c.c. of water. 2 c.c. of the 
sample are shaken in a closed test-tube with 5 c.c. of this reagent. 
The following results are noted: Citral, bright red Hquid 
quickly changing to a white floating material; Citronellal, 
bright yellow not quickly fading; Limonene, transient flesh 
tint fading to white. 

The oil may also be determined directly. 20 c.c. of the sam- 
ple are introduced into a milk-testing bottle (seepage 203), i c.c. 
of diluted hydrochloric acid (i : i) added, and then 25 c.c. water, 
previously warmed to 60°. The liquids are mixed and allowed 
to stand for 5 minutes in water at 60°. The tube is whirled in 
the milk-centrifuge for 5 minutes, warm water added until the 
oil is brought into the graduated neck, then again whirled for 
a few minutes, allowed to stand in water at 60° for a short 
time and the volume of separated oil read oft*. If the volume 
is over 2 per cent., add 0.4 as a correction for oil in solution; if 
between i and 2 per cent., add 0.3 for this correction. Of 
course, these tubes must be operated in pairs. The oil thus ob- 
tained may be used for several tests. To obtain the percentage 
in the original extract, multiply the observed volume by 0.86 
(specific gravity of lemon oil at 15.5°) and divide by the specific 
gravity of the extract. 

Alcohol. — If the extract contains no other substances than 
oil, alcohol and extractives of the lemon-peel, the specific gravity 
may be taken and the equivalent proportion of alcohol cal- 
culated from the usual tables. Deducting from this the per- 
centage of lemon oil, the remainder will be alcohol. If an 
absolute determination of alcohol is desired, 50 c.c. of the sample 
should be diluted to 200 c.c. with water, the mixture shaken 
with 5 grams of magnesium carbonate, filtered through a dry 
filter, distilled, and the percentage of alcohol determined by the 
specific gravity. 



FRUIT JUICES, SIRUPS, JELLIES AND JAMS 327 

Methyl alcohol is detected by the test given in connection with 
the examination of alcohohc beverages. The absence of formal- 
dehyde should be ensured before making this test. For the 
method of detecting it see page 83 and for a method of removing 
it before testing for methyl alcohol, see under "Alcoholic 
Beverages." 

The tabulated results of a systematic examination of lemon 
extract sold in Massachusetts in 1901, reported by Leach, ^^ show 
the following range of composition. The polarization is in 
200 mm. tube and on sugar scale: 

Standard. Adulterated. 

Polarization, 17.0-30.8 0.0-14.0 

Lemon oil, 5.0-9.1 0.0-4.1 

Specific gravity (15.6°), 0.8268-0.8296 0.8416-0.9937 

Alcohol per cent, by volume, 80.0-86.8 4.49-87.5 

Two of the samples included under "standard" contained 
added color, turmeric in one and dinitrocresol in the other. 

One adulterated sample, not included in the above summary, 
gave a polarimetric reading of — 8.0. It contained invert sugar. 
Another sample, also, not included above, gave a reading of 
27.0. It contained sucrose. The adulterated samples were 
mostly colored, azo-dyes and dinitrocresol being most frequently 
used. A considerable number of the samples contained no 
lemon oil. 



FRUIT JUICES, SIRUPS, JELLIES AND JAMS 

Fruit juices are made by pressing the fruit and straining the 
liquid portions. Jellies are prepared by boiling the juice, with 
or without addition of sucrose, until the mass sets on cooling. 
The setting is due principally to pectin, a non-nitrogenous 
body bearing some analogy to the carbohydrates. Jams are 
made by concentrating the juice by boiling, without straining, 
and adding considerable sucrose. 



328 FOOD ANALYSIS 

The composition of these products is shown in the following 
table from the analyses of Tolman, Munson and Bigelow®'^: 

Fruit Juices. 

(Prepared by adding a convenient amount of water, cooking until the fruit 
is soft and straining through muslin.) 

ToTAt Reducing Polar, at 18° 

Solids. Ash. Sugar. Sucrose. Sugar Scale. 

Apple (pippin), 7.95 0.47 4.00 1.18 —3.0 

Crab-apple, 5.62 0.20 2.56 1.03 — i.o 

Grape (cultivated), .. . 8.83 0.57 5.10 0.89 — 1.2 

Blackberr}', 8.54 0.52 4.34 0.00 — 1.5 

Huckleberry, ^^-33 0.40 11. 21 0.89 — 3.2 

Peach, 8.90 0.45 — 4.59 4.0 

Pear(Bartlett), 11.65 0.45 5.87 1.18 —4.8 

Plum (Damson), 12.72 0.63 4.86 0.51 2.0 

Jellies. 
(Fruit juices concentrated, strained and sucrose added.) 

Total Solids. Ash. Red. Sug.ar. Sucrose. 

Apple (pippin), 59.18 0.22 20.78 33.04 

Crab-apple, 63.28 o.ii 34-93 23.68 

Grape (cultivated), 63.66 0.45 32.29 SO-S^ 

Blackberr)-, 59.63 0.33 12.51 44.90 

Huckleberry, 63.02 0.28 32.29 30-52 

Peach, 69.98 0.21 8.75 56.59 

Pear (Bartlett), 69.12 0.34 6.58 58.46 

Plum (Damson), 45-56 0.68 19.18 22.67 

Jams. 

(Moderate concentration and addition of sucrose.) 

Total Solids. Ash. Red. Sugar. Sucrose. 

Apple (pippin), 63.22 0.20 25.52 29.11 

Crab-apple, 41.82 0.27 14.80 23.04 

Grape (cultivated), 56.64 0.48 33-44 ^^-33 

Blackberry, 55-42 0.48 18.77 29.00 

Pear (Bartlett), 61.52 0.28 13-20 33-74 

Plum (Damson), 5^-43 o-54 28.29 9.70 

The proteids in the juices are much below i per cent.; the 
acidity expressed as sulfuric acid is also below i per cent., but 
in the grape is slightly over 0.9. The sucrose added to the jellies 
and jams has been largely inverted by the fruit-acids, hence 
the reducing sugar is greatly increased. 



FRUIT JUICES, SIRUPS, JELLIES AND JAMS 329 

Ripe cranberries contain notable amounts of benzoic acid. 
G. F. Mason,^^ who has recently made a careful study of this, 
found about i part of benzoic acid to 2000 parts of the fresh 
pulp, a quantity sufficient to act as a preservative. The occur- 
rence of borates in many fruits must not be overlooked (see 
under "Cider"). 

Adulterations. — The adulterations of these articles are 
frequent and extensive. Occasionally no true fruit-ingredient, 
except water, is present. A cheap, so-called strawberry jam 
has been sold consisting of apple pulp, glucose, fuchsin, sul- 
furic acid (for tartness), grass seed (to imitate the achenes of the 
fruit), sodium benzoate and artificial flavors. Apple pulp is 
frequently used as a basis, also starch jelly. Other vegetable 
pectins, such as agar, may be used, but gelatin has not been 
satisfactory. Saccharin or other artificial sweetener is some- 
times used in complete replacement of sucrose. Saccharin 
may also be present merely as a preservative. 

Analytical examinations will include particularly tests for 
added color, preservative, glucose, starch-jelly and artificial 
flavors. The determinations of ash, total solids, proteids and 
acidity are not usually important. If required they may be 
made by the standard methods. The total solids will be best 
taken by making a definite dilution and evaporating this on a 
shallow broad glass dish. The low-pressure oven (page 30) 
will be especially suitable. Added color is to be sought ac- 
cording to the methods on pages 64 to 75. It must not be for- 
gotten that at present several natural vegetable colors are being 
used, such as cochineal, lichin colors, fustic and chlorophyl, 
hence the special examinations indicated for these must be made 
in addition to the double-dyeing test. 

Saccharin, salicylic acid, benzoates and abrastol are detected 
by acidulating a portion of the sample and shaking out with 
the mixture of petroleum spirit and ether, or with ether alone. 
See pages 86 and 362. 
29 



330 FOOD ANALYSIS 

For the determination of glucose see page 126. The glucose 
used in the articles may have a ])olarimetric reading of 150 
on the sugar scale, and Leach's formula must be modified as 
there indicated. 

Lemon Sirup. — This is a mixture of lemon juice with sugar. 
The composition of samples of commercial sirup and lemon 
juice is given by Borntraeger. 

Lemon Juice 

Ripe Fruit. Unripk Fruit. 

Citric acid, 7.25 7.70 

Reducing sugar, 0.75 0.21 

Sucrose, 0.19 0.78 

Ash, 0.39 0.49 

Total solids, 8.87 9.30 

Lemon Sirup 

Pure Adulterated. 

Citric acid, 14.40 5.42 

Tartaric acid, 0.00 10.70 

Reducing sugar calculated as dextrose,. .30.10 38.42 

Sucrose, 0.00 0.00 

Ash, 0.32 0.72 

Total solids, 81.92 80.56 

The reducing sugar may result from the inversion of sucrose. 
The price of tartaric acid, as compared with citric, leads to 
the use of the former in imitation sirups. Other acids, such 
as sulfuric, may be used. The adulterations, in addition to 
this substitution, will be similar to other fruit juices, namely, 
imitation coloring, imitation sweetening, and, possibly, pre- 
servatives. The methods of recognizing these additions are 
described in the section on "General Methods" and under 
''Alcoholic Beverages." 

Orange juice and orange sirup will be subject to the same 
adulterations as the products from lemon, and are to be tested 
in the same way. 

Farnsteiner & Stueber have found the following range of 



FRUIT JUICES, SIRUPS, JELLIES AND JAMS 33 1 

composition in orange juice known to be pure. The figures 
are grams per loo c.c, except as noted. 

Total solids, io-73 10.92 

Citric acid, 1.19 1.79 

Total sugar (after inversion, calculated as invert 

sugar), 7.65 8.26 

Ash, 0.41 0.52 

Alkalinity of asli'(c.c. of -^— acid), 5.40 7.20 

Polarization, — o.ii +2.45 

There were small amounts of proteids, phosphates and 
glycerol. 

The artificial flavors employed in the preparation of these 
articles are mostly alcoholic solutions of esters of acids homol- 
ogous with formic. Ethyl acetate is often present as a basis 
material; pentyl acetate and butyrate are common. 

Some information as to the esters present in a sample may 
be obtained by fractional distillation in an apparatus such 
as shown in figure 29. Several fractions should be collected, 
and the odor of each carefully noted. The esters may also 
be saponified by strong sodium hydroxid solution, the odor 
of the alcohol produced noted, as well as the odor of the acid 
obtained by decomposing the sodium salts with sulfuric acid. 

The following selection from published formulas for arti- 
ficial flavors will show^ the general characters of them. The 
figures are the relative proportions by volume to 100 parts 
of alcohol as a solvent. 

Pineapple: chloroform, i ; aldehyde, i ; ethyl butyrate, 5 ; 
pentyl butyrate, 10. 

Strawberry: ethyl nitrite, i; ethyl acetate, 5; ethyl formate, 
i; ethyl butyrate, 5; pentyl butyrate, 2; pentyl acetate, 5. 

Raspberry: ethyl nitrite, i ; aldehyde, i ; ethyl acetate, 5 ; 
ethyl formate, i ; ethyl butyrate, i ; ethyl benzoate, i ; ethyl 
enanthylate, i ; ethyl sebacate, i ; methyl salicylate, i ; pentyl 
acetate, I ; pentyl butyrate, i. 



332 FOOD ANALYSIS 

Citric acid being often replaced by tartaric, and tartaric 
sometimes substituted by cheaper acids, the detection of the 
tartaric and the determination of it and citric acid are very 
important. 

Dcfcclion oj 'Jarlaric AcidJ^' — With dry materials, mix a 
little of the sample with a small fragment of resorcinol, then 
with a few drops of sulfuric acid and heat slowly. A bright 
red is produced with tartaric acid. Fruit-juices may be evapo- 
rated to dryness and the residue tested,. or the acid potassium 
tartrate may be precipitated by the method given under de- 
termination of tartaric and this precipitate tested. Starch 
must not be present. Phosphates and alkalies do not interfere. 

Determination oj Tartaric Acid.^^ — loo c.c. of the fruit juice 
are mixed with 2 c.c. of acetic acid, a few drops of a 20 per 
cent, potassium acetate solution and 15 grams of finely-pow- 
dered pure potassium chlorid added, shaken until the mate- 
rials are dissolved, and then 20 c.c. of alcohol and the liquid 
stirred actively for i minute, rubbing the w^alls of the beaker 
with the glass rod. The liquid is allowed to stand for 15 
hours at room temperature, collected, filtered in a Gooch 
crucible with a little asbestos felt, using a filter pump. The 
washing liquid should be made up of 20 c.c. alcohol, 100 c.c. 
water and 15 grams potassium chlorid. The beaker is rinsed 
a few times with a few c.c. of this solution and the precipitate 
is also washed with some of it, but the whole amount of wash- 
ing liquid used should not be more than 20 c.c. The pre- 
cipitate and filter are washed, with water, back into the beaker, 
brought to the boiling point, and while hot titrated with -^ 
sodium hydroxid, using phenolphthalein. To the amount of 
alkali used 15 c.c. should be added for the acid tartrate that 
is not precipitated, i c.c. of the alkali is equivalent to 
0.0075 gram tartaric acid. Hardened filters might replace the 
filter suggested. 

Determination oj Citric Acid.^^ — 50 c.c. of the juice are evapo- 



CATSUP, TABLE ACCESSORIES AND DESSERTS 1,1,1, 

rated on the water-bath to small bulk. Alcohol is added 
to this residue, slowly with constant stirring until no further 
precipitation occurs. This will require about 80 c.c. The 
precipitate is collected on a filter, washed with alcohol, evapo- 
rated until the alcohol is removed, the residue taken up with 
water and made up to 10 c.c. in a graduated cylinder. 5 c.c. 
of this are mixed with 0.5 c.c. acetic acid, and then, drop by 
drop, saturated lead subacetate solution. If a precipitate 
appears which is dissolved by heating and reproduced on 
cooling, citric acid is present. Heat the liquid to boiling, 
filter if necessary, wash with boiling water. On cooling, the 
lead citrate will separate. It should be collected on a hardened 
filter, w^ashed into weak alcohol, dried and weighed. The 
weight multiplied by 0.385 will give citric acid. If tartaric 
acid is present, the juice must be neutralized first by potas- 
sium hydroxid in order to prevent the precipitation of acid 
potassium tartrate. 

TABLE ACCESSORIES AND DESSERTS 

Very many articles are included under this head, mostly 
vegetable products. The composition of them is given in 
cook-books. They are liable to adulteration in many ways. 
The basic materials may be imitated by cheaper products, 
colors and preservatives may be added. It must not be for- 
gotten that small amounts of salicylates and borates occur in 
many vegetable substances, and further that some of the basic 
material, such as the tomato-pulp for catsup, may be mixed 
with preservatives by the wholesaler in order to keep it, and 
thus small amounts be found in the finished product, although 
the maker of the latter may not be aware of it. 

For the ordinary table accessories, the methods of analysis 
will be directed to the detection of added color, preservative 
and in some cases artificial flavors and artificial sweetening 
(e. g., saccharin and glucose). The preservatives, exclusive 



334 FOOD ANALYSIS 

of vinegar and common salt, are usually boric acid, salicylic 
acid or sodium benzoate, but there is liability to the use of 
lluorids, bctanaphthol, and abrastol. 

Gelatin, starch and agar are used as fillers. Some materials, 
e. g., pickles and canned peas, are liable to contain small 
amounts of copper. 

The methods of detection of most of these ingredients are 
given elsewhere; gelatin and agar require special notice. 

Agar (agar-agar) is derived from marine alga.\ It forms 
with water a stiff jelly that does not melt as readily as that 
from ^ gelatin. It is used as a thickening agent in milk and 
cream, in desserts and as a substitute for white of egg. 




Fig. 52. — Arachnoidiscus Ehrenhergii. X 100. The smaller oval diatoms are 

a species of Cocconeis. 

Commercial agar almost always contains diatoms. One 
characteristic form is Arachnoidiscus Ehrenhergii. (See figure 
52.) The diatoms may be obtained by oxidizing the organic 
material with a mixture of nitric and sulfuric acid or nitric 
and hydrochloric acids. ^loist materials should be well dried 
but not powdered. The diatoms will be found by examining 
the residue with a power of about 100 diameters. 

Gelatin. — For the detection of this the following process has 
been proposed: The material is boiled with water, filtered, 
the filtrate boiled with excess of potassium dichromate, cooled, 
and a few drops of sulfuric acid added. If gelatin is present, 
a flocculent precipitate will be formed. 



EGG-SUBSTITUTES 335 

It is probable that the reaction of gelatin with formaldehyde 
could be utilized in these examinations. 

Gelatin in mass can be at once distinguished from starch 
and agar by its odor on heating to the charring point. 

Ice Cream and Water Ices are subject to adulteration with 
starch, gelatin and agar. The so-called "Hokey-Pokey" 
sold in slum districts is usually made with agar on account of 
less liability of the jelly to melt. This and similar articles are 
apt to be unclean, containing bodies of insects and other filth. 
Microscopic examination will be required for these. The 
general adulterations above enumerated will be found also. 
Formaldehyde is sometimes used in ice cream. It is to be de- 
tected by the methods given under milk. 

Cakes and Pastry may contain fillers (gelatin, starch and agar) , 
egg-substitutes, sometimes merely color to simulate egg-yolk. 
The imitation chocolate-paste noted on page 64 is often used. 

For special processes for detection of eggs see under "Egg- 
Substitutes." 

EGG-SUBSTITUTES 

Several forms of egg-substitutes are common. Some consist 
of starch and sugar with coloring matter; others contain egg- 
albumin, but no yolk. Desiccated eggs are noAv a commercial 
article. These may have added color. The colors commonly 
used are turmeric, annatto, and coal-tar dyes, the latter being 
generally azo-colors, but sometimes nitro-colors. 

For the detection of colors see page 73. The recognition 
of egg-yolk as an ingredient in foods has been investigated by 
Winton & Bailey,^'^ applying especially methods of Juckenack 
and Pastenack,^'"' which depend on determining the fat and 
lecithin of the egg-yolk. The lecithin is determined in the form 
of phosphoric oxid. For the determination of the lecithin phos- 
phorus, Winton & Bailey recommend Juckenack's modifica- 
tion of Wichelhaus' method, as follows: 



;^J,(J lOOD ANALYSIS 

A weighed amount (about 30 grams) is extracted with ab- 
sokite alcohol in an apparatus so arranged that the material 
can be kept not lower than 55°. A few pieces of pumice should 
be put in the flask in which the solvent is heated. When the 
extraction seems complete, the solution should be saponified by 
5 c.c. of a 4 % solution of pure potassium hydroxid in alcohol. 
The alcohol is distilled otT, the residue transferred to a platinum 
dish by aid of hot water, mixed with some asbestos, dried on 
the water-bath and charred. The char is treated with dilute 
nitric acid, filtered, the residue washed with water and returned 
with the filter paper to the dish, treated again with nitric acid, 
filtered, the filtrates mixed and the phosphoric acid determined 
in the usual way. It is principally derived from the lecithin of 
the egg-yolk. 

As egg-yolk contains a much higher percentage of fat than 
flour, the ether-extract of many food articles will also be of 
value in determining the presence of eggs, but it must be borne 
in mind that to many articles, milk, butter or other fats are added. 
The following data are from a compilation by Winton & Bailey 
of the original results of Juckenack & Pastenack. The German 
pound used in making the mixtures is about 468 grams. The 
figures are percentages of phosphoric oxid and ether-extract 
on the original mixture. 

Phosphoric Oxid. Ether Extract. 

Flour with no eggs, 0.0225 0.66 

I pound flour with i egg, 0.0513 1.56 

I pound flour with 3 eggs, 0.1044 3-24 

I pound flour with 12 eggs, 0.2875 7-9-4^ 

For the detection of azo-colors in pound cake, sponge cake, 
and similar articles, it is often sufficient to touch a freshly-cut 
surface with hydrochloric acid, when the rose-pink stain will 
show the dye. 



CIDER 337 



ALCOHOLIC BEVERAGES 

CIDER 

Cider is the juice of apples either before or after ferment- 
ing; when the alcohol is in considerable amount, the liquid is 
often called "hard cider." Cider differs from wine in con- 
taining no tartrates, and larger amounts of malates and calcium 
compounds. Pear cider, often called "perry," contains more 
sugar than apple cider, and, therefore, yields more alcohol when 
fully fermented. Many other fruits will yield fermentable 
juices more or less analogous to true cider. 

The following analyses by Browne" show the range of com- 
position of fresh and fermented apple juices. The figures are 
grams per loo c.c. 

Apple Juice. Fermented Juice. 

Total solids, ii. 36-16. 85 1.93-3.26 

Invert sugar, 5.47-10.52 0.19-0.89 

Sucrose, i .83- 7.05 

Free malic acid, o.io- 1.24 0.21-0.30 

Ash, 0.23- 0.37 0.23-0.36 

Acetic acid, . . 0.2 i-i .96 

Alcohol, . . 4.26-6.85 

Fresh apple juice is always strongly levorotatory, and retains 
some of this power after fermentation and even after conversion 
into vinegar. Several observers have shown the presence of 
borates in fruits. The following data were obtained by Allen & 
Tankard ^^ by the method given in connection with the analysis 
of alcoholic beverages. 

Per Cent. Orthoboric Acid. 

Apple, 0.009-0.013 

Pear, 0.007-0.016 

Quince, 0.016 

Pomegranate, 0.005 

Grapes, 0.004 

Cider, 0.004-0.017 grams per 100 c.c. 

30 



2,;^S FOOD ANALYSIS 

The provisional standards for cider offered by the A. O. A. C. 
are: 

Alcohol, not over 8.0 per cent. 

Ash, not less than 0.2 " 

Apple solids, " " " 1.8 

Adulterations. — The usual adulterations of cider are 
dilution with water, addition of sodium carbonate or lime in 
order to correct acidity, and addition of preservatives. The 
ash of cider contains no sodium. When heated, it volatilizes 
at a comparatively low temperature, and imparts to flame a 
pure potassium color. The dilution of cider with ordinary 
water containing even a small proportion of sodium may be 
detected by this test. The proportion of ash to the original 
solids may furnish some indication of the nature of a sample 
under examination. In unfermented cider the ash will range 
from 2 to 5 per cent, of the total solids. If the sample be fer- 
mented, an allowance must be made for the loss in solids. (See 
under 'Xider Vinegar.") Caramel or coal-tar colors may be 
present in dilute samples. Sodium carbonate may be added to 
diminish acidity. It will appear in the ash. Preservatives 
are often used, the most frequent being salicylic acid, sulfites, 
sodium benzoate and formaldehyde. The natural occurrence 
of borates in small amount must not be overlooked. 

The analysis of cider is conducted by the methods given for 
alcoholic beverages. 

SPIRITS 

Spirits are the liquors obtained by the distillation of alcoholic 
liquids. The latter arc the results of fermentation of saccha- 
rine infusions derived from barley, oats, wheat, maize, rice, 
potatoes, or from vegetable juices. The distilled liquor con- 
tains water, ethyl alcohol along with a small proportion of its 
homologues (fusel oil), aldehydes, acetic acid, and various 
esters. The amount and nature of these associated bodies 



WHISKEY 339 

depend upon the nature of the fermented material and the 
method of manufacture. The character of the distilled spirit 
is further modified by the addition of various flavoring m^ate- 
rials. 

WHISKEY 

WTiiskey is the spirit distilled from fermented grain or po- 
tatoes. In some cases malted grain is used, but more usually 
a mixture of malted and unmalted grain is employed. Spirit 
from raw grain usually contains a larger proportion of fusel oil. 
The grain commonly employed in the United States is rye and 
maize, but wheat is also used to a considerable extent and glu- 
cose is a frequent addition. The weak spirit (so-called "low 
wine") which is obtained by distillation is usually redistilled, by 
which it is obtained stronger and less charged with fusel oil. 
When only malted grain is used, the liquid is sometimes distilled 
in small stills, called '^pot heads," and at once set aside to age 
without redistillation. 

Freshly distilled whiskey is colorless and of disagreeable 
flavor. It is often stored in sherry casks, and allowed to remain 
for a considerable time until it has aged or ripened, the pro- 
cess consisting in part in the conversion of the fusel oil into 
various esters of agreeable smell and taste. At the same time 
a small amount of tannin and other matters are extracted from 
the cask, and the whiskey acquires an amber or yellow color, 
which is frequently heightened by the addition of caramel, 
logwood, catechu, tea infusions and prune juice. Old whiskey 
has an acid reaction, due to the presence of a small amount of 
acetic and possibly other acids. The acidity increases with 
age, but is rarely over o.i per cent, expressed as acetic acid. 

The U. S. Pharmacopeia"^ defines whiskey to be "a distillate 
from the mash of fermented grain, as maize, wheat, or rye. It 
is an amber-colored, slightly acid liquid. The specific gravity 
should be not more than 0.930 nor less than 0.917, corresponding 



340 FOOD ANALYSIS 

to an alcoholic strength of from 44 to 50 per cent, by weight 
or 50 to 58 per cent, by volume. If 100 c.c. be slowly evaporated 
in a tared capsule in a steam-bath, the last portion should not 
have a harsh or disagreeable odor (absence of more than mere 
traces of fusel oil). The residue, dried at 100°, should not 
weigh more than 0.21 gram, have no sweet or distinctly spicy 
taste, should dissolve almost completely in 10 c.c. of cold water 
to form a solution not more deeply colored than light green by a 
few drops of ferric chlorid solution (absence of more than traces 
of oak tannin). 100 c.c. of whiskey should not require more 
than 12 c.c. ^^ sodium hydroxid to render it distinctly alka- 
line." 

In Scotland and Ireland the drying of the malt takes place 
in kilns in which peat is used as fuel, and the spirit whiskey 
made from it has a strong smoky flavor. This is often im- 
itated by the addition of two drops of creasote to the gallon of 
spirits. A variety of whiskey is sometimes made by distilling 
cider, and is known as apple- whiskey or apple-brandy. 

Whiskey is occasionally adulterated wdth methyl alcohol. 
Cayenne pepper is also said to be added in order to give greater 
warmth of taste, and thus enable a weak spirit to be sold for a 
strong one. In some cases it appears to have been added 
simply as a flavor. 

Lead, copper, and zinc have been found in w^hiskey, and are 
probably derived from the apparatus employed in the dis- 
tillery. They are also said to have been added directly. 

The follow^ing are some results of analyses of commercial 
whiskey by Allen: 

Commercial Commercial 
Scotch Whiskey. Irish Whiskey. 

Specific gravity, 0.9416 0.9408 

Alcohol (percentage by weight), 3905 39-3° 

Secondary constituents, expressed in grains 
per imp. gallon: 

Free acid, as acetic, 10.2 6.8 

Ethers in terms of acetic ether, 46.5 23.1 

Higher alcohols in terms of am\'l alcohol, 89.6 78.8 

Aldehyde, Trace. Trace. 

Furfural, " 



BRANDY — GIN RUM 341 

BRANDY 

Brandy, also called French brandy or '^ cognac," is the 
spirit obtained by distilling wine. An inferior quality is 
manufactured from skins and stalks (''marc") of the grapes. 
Such brandy usually contains more fusel oil than that made 
from wine. So-called British brandy is made from grain 
spirit to which is added flavoring esters, such as ethyl acetate, 
pelargonate and nitrate, bitter almonds, spices, and caramel. 
Freshly distilled brandy is colorless, but on standing in casks 
it dissolves a minute quantity of tannin and other bodies and 
acquires an amber tint. It is also frequently colored with 
caramel. 

The provisional standard of A. O. A. C. for brandy is: 

Alcohol by volume, 44~"55 P^r cent. 

Total solids, not over 0.35 " 

GIN 

Gin, and the varieties known as Hollands or Schnapps, are 
usually prepared by redistilling grain spirit which has been 
flavored with various bodies, among which may be mentioned 
juniper berries or oil of juniper, turpentine, coriander and car- 
damon seeds, capsicum, orris, angelica, and calamus roots. 
Gin is without color and is comparatively free from fusel oil 
and the associated bodies found in brandy and whiskey. 

The A. O. A. C. standard requires not less than 40 per cent, 
of alcohol by volume. 

RUM 

Rum is the spirit obtained by distilling the fermented juice 
of the sugar-cane, or, more commonly, by distilling fermented 
molasses. The flavor of rum is due largely to the presence 
of ethyl butyrate and ethyl formate. It is colored either by 
long keeping in casks, or by the addition of burnt sugar. Much 
of the commercial article is made from grain spirit to which 



342 FOOD ANALYSIS 

has been added butyric acid or butyric or acetic esters. Pine- 
apple and tannin-containing materials are also added. Ac- 
cording to Allen, the presence of formates might serve to 
distinguish genuine rum from the factitious product. The 
rum should ])e evaporated almost to dryness with a slight 
excess of sodium hydroxid and the residue treated with phos- 
phoric acid and distilled. The distillate from genuine rum 
will strongly reduce silver nitrate, and give the other reactions 
for formic acid. 

The A. O. A. C. standard for rum gives a range of alcohol 
by volume from 44 to 55 per cent. 

MALT LIQUORS 

These are, strictly speaking, infusions of malt, fermented 
by yeast, and rendered bitter by the addition of hops. Hop- 
substitutes are little used unless the price of hops advances, 
when quassia, chiretta, and aloes may be employed. The 
common substitutes for malt are unmalted cereals, glucose, 
and starch. 

Two methods of fermentation are in use for the prepara- 
tion of beers. The "high" or "surface" fermentation, em- 
ployed for English beers, takes place at a temperature of 15° 
to 20°, and is completed in from 4 to 8 days. The "low" 
or "bottom" fermentation, employed in Germany, takes 
place at a temperature of from 4° to 8°, and requires from 
20 to 24 days for completion. In this process the yeast 
remains at the bottom of the vat. In each of these there is 
a predominance of particular species of yeasts, and unless 
carefully selected and cultivated, the yeast mass will contain 
species producing irregular and often objectionable fermenta- 
tion-products. In this way malt liquors may acquire unpleas- 
ant bitterness or odor, or troublesome turbidity. 

The principal constituents of beer are as follows: 

Volatile. — Water, alcohol, acetic and other acids. 



MALT LIQUORS 343 

Fixed. — (Extract.) Sugar, chiefly maltose, dextrin, and 
similar bodies, proteids, glycerol, lactic acid, succinic acid, 
bitter principles, and mineral matters, chiefly phosphates. 

The following are the principal varieties of malt liquors: 

Ale, made from a light-colored malt, usually with addition 
of glucose, and a large proportion of hops. So-called "mild 
ales" are usually sweeter, contain a larger proportion of 
alcohol, and are less bitter. 

Porter and Stout are principally distinguished from the 
above by their flavor, derived from the use of a certain pro- 
portion of roasted malt. They also contain less hops. 

A]e, porter, and stout are made by the high fermentation 
process. Lager or German Beer is prepared by the low 
fermentation process and contains less alcohol, more sugar, 
dextrin, and nitrogenous matter, and is more highly charged 
with gas. Lager beers are liable to undergo a second fer- 
mentation unless kept at a low temperature. 

So-called Weissbier is light-colored and about half the 
strength of lager beer. Rice is often used in its manufac- 
ture. 

Root Beers and Meads. — Solutions of cane-sugar flavored 
with herbs and roots are much used for the manufacture of 
home-brewed beers. These are subjected to a brief fermenta- 
tion in closed vessels, and, as a rule, but insignificant propor- 
tions of alcohol are formed. 

Adulteration. — The chief adulteration of malt liquors 
consists in the addition of substances other than malt and of 
preservatives. The use of glucose is very common, and may 
possibly be detected by the presence of gallisin, which is a 
usual constituent of the commercial article. The substitu- 
tion of any considerable proportion of glucose, rice, or starch 
for the barley will be indicated by the lowered proportion of 
proteids, ash, and phosphates. Glucose is cspecialh' indicated 
by higli proportion of sulfates to total ash. 



34 + 



FOOD ANALYSIS 



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WINE 345 

The addition of preservatives, especially salicylic acid, 
sodium fluorid, sodium silicofluorid, and of sulfites is very 
common. Sodium bicarbonate is also added in order to cor- 
rect acidity. The quantity of chlorids may, at times, be con- 
siderable, due either to the addition of salt, or to the presence 
of chlorids in the water used in making the mash. The direct 
addition of salt is probably infrequent. 

The following recommendations as to standards of composi- 
tion of beer were made in 1897 to the Association of Official 
Agricultural Chemists by the referee on food adulteration : 

''The glycerol content of beer should not be less than 0.4 
gram per 100 c.c. The ash should not be less than 0.12 nor 
greater than 0.30 gram per 100 c.c. The presence of less than 
o.io gram indicates that some malt substitute low in ash, such 
as starch, has been used in. the preparation of the beer, while 
if the ash content be greater than 0.30 gram per 100 c.c, and 
the volatile acids, calculated to acetic acid, less than 0.075 gram 
per 100 c.c, it is probable that an excess of acid has been neu- 
tralized by sodium carbonate, and the ash of the beer should 
be examined for both sodium and carbonic acid. The phos- 
phoric oxid should not be less than 0.05 gram nor greater than 
0.10 gram per 100 c.c If less than 0.05 gram, it is probable 
that a portion of the malt has been replaced by starch or similar 
substance." 

WINE 

Wine has been defined to be the fermented juice of the grape 
with such additions as are essential to the stability or keeping 
of the liquid. The method of preparation is, briefly, as follows: 
The grapes are crushed, the stem being removed in the case 
of the better grades of wine, and the juice expressed. The 
juice or "must" is sometimes allowed to stand in contact with 
the skins for several days in order to extract additional "bou- 
quet." In the case of red wines, the expression of the juice 



34^ FOOD ANALYSIS 

and removal of the skins do not take place until the fermentation 
is practically completed. The juice of most varieties of grapes 
is colorless, but in the presence of alcohol formed by the fer- 
mentation the red coloring-matter of the skin is extracted; red 
wine contains a greater proportion of tannin than white wine. 
The chief fermentation of the wine usually takes place in from 
four days to several weeks, according to the temperature at 
which it is conducted. After this, the liquid is drawn off into 
casks, where a secondary quiet fermentation takes place. 
The wine is then allowed to age or ripen, a process which in- 
volves chiefly direct oxidation, and during which potassium 
acid tartrate is deposited, along with a considerable proportion 
of the coloring-matter, and, by the interaction of the alcohols 
with the acids and other constituents present, various esters 
are formed which give flavor and bouquet. 

The yeast that ferments the must is found on grape skins. 
There are many varieties, some of which produce special flavors, 
and by the application of these in special cases the flavor of the 
wine may be modified. 

Wines prepared as above usually contain very little sugar, 
and are termed dry wines, as distinguished from ''full-bodied" 
or sweet wines. Some wines are prepared by adding to the 
must a certain proportion of alcohol, which causes the fermenta- 
tion to cease before the complete conversion of the sugar is 
effected. Port and sherry are manufactured in this way. 

Champagne is usually prepared as follows: The pressed 
grapes are fermented as rapidly as possible until but little 
sugar is left. The clarified wine is blended with other wine 
to bring it to the quality desired, and pure sugar (about 2 per 
cent.) is added and the liquid placed in strong bottles, which 
are tightly stoppered and placed horizontally until fermenta- 
tion is completed, and then with the necks downward, and, 
as the wine clarifies, the yeast-sediment collects on the stop- 
per. This is promoted by frequent turning and manipula- 



WINE 347 

tion of the bottle. The bottle is then skilfully uncorked and 
a small portion of the wine, carrying with it the sediment, 
removed. The space so emptied is filled by the addition of 
wine and a certain proportion of so-called liqueur, and the 
bottle recorked and wired. The operations are performed 
so quickly that there is but little loss of carbon dioxid. The 
liqueur consists of a mixture of sugar, wine, and cognac. Cham- 
pagne is sometimes prepared by adding the liqueur to the fer- 
mented Avine and charging the liquid with carbon dioxid under 
pressure. 

The normal constituents of wine are water, alcohol and its 
homologues, acetic acid, succinic acid, various compound 
ethers, sugar, gum, pectin, glycerol, tannin, coloring-matters 
(in red wine), tartaric acid, calcium or potassium tartrates, 
phosphates, and other mineral matter. 

The sugar in wine is apt to be chiefly levulose, dextrose 
being more readily fermentable. 

The table on page 348 gives the composition of must and 
wines from various sources expressed in grams per 100 c.c. 
The data are derived in most cases from the examination of a 
great many samples. 

Adulteration. — The fact that the composition of wine 
varies within notable limits renders it impossible to assign ab- 
solute standards and allow a margin for the addition of water 
and other substances without so far changing the composition 
as to enable the chemist to determine whether a given sample 
is or is not genuine. Usually it can only be stated that the 
sample conforms in composition to that of genuine wine. 

In some cases additions to the wine or must are regarded 
as legitimate. Thus, it has been found that a certain propor- 
tion of acid to sugar in the must is best adapted to the pro- 
duction of good wine; and in cases in which this proportion 
does not obtain, it is the practice, in some localities, to make 
such additions as are necessary to bring these constituents 
within the proper limits. 



348 



FOOD ANALYSIS 




WINE 



349 



The following conclusions were arrived at by an official 
German commission: 

The total extract of wines should not be below 1.5 grams 
per 100 c.c. After deducting the non-volatile acids, the ex- 
tract should be at least i.i grams per 100 c.c. 

Natural wines usually contain a close approximation of i 
part ash to 10 parts of extract. 

The proportion of free acid calculated as tartaric acid ap- 
pears not to exceed one-sixth of the total volatile acid. 

Genuine wines will not contain less than 0.14 gram of ash 
nor more than 0.05 gram of sodium chlorid in 100 c.c. 

U. S. Standard. 

Alcohol by volume 7 to 10 per cent. 

Sodium chlorid, not over o.i gram in 100 c.c. 

Potassium sulfate, not over ...0.2 '' " << 

Volatile acids ^ ^ ^ . 

, , ^ , Red wme 0.14 gram to 100 c.c. 

calculated as V,^ . . .... 

1 White wme.. 0.12 '' '' " 

acetic J 

Dry Wine. 

Sugar, less than i .0 gram in 100 c.c. 

Grape solids, red wine, not less 

than 1.6 

Grape solids, white wine, not 

less than 1.4 " " 

Grape ash, red wine, not less 

than 0.16 

Grape ash, white wine, not less 

than 0.13 

Sweet wine. 

Sugars, not less than i.o '' '' 

Grape ash, red wine, not less 

than 0.16 

Grape ash, white wine, not less 

than 0.13 



350 FOOD ANALYSIS 

The plastering of wines consists in sprinkling the grape or 
must with plaster-of-Paris, with a view of securing a quicker 
fermentation, better color, and keeping quahties. Plastered 
wine shows but a small increase in ash, but the wine from 
plastered must shows a large increase in the form of potas- 
sium sulfate rather than calcium sulfate. If a wine unusually 
rich in sulfates and potassium compounds contains little or 
no tartar, it must have been plastered, and the absence of alka- 
linity in the ash will confirm this. 

Sulfurous acid is often present in new wines, from the use of 
sulfites or burning sulfur for the purpose of disinfecting the 
casks. 

The additions to wine commonly practised are sugar, glu- 
cose, honey, glycerol, tartaric acid and other vegetable acids, 
gums, tannin, vegetable astringents, coloring-matters, flavor- 
ing ethers, salicylic acid and other preservatives. In order to 
increase the sugar, total extract and free acid, figs, dates, tama- 
rinds, and St. John's bread are frequently employed. Dried 
raisins are largely used for the manufacture of imitation wines. 

A form of adulteration is the decolorization of red wine by 
the use of charcoal or possibly potassium permanganate, the 
product being sold as a genuine white wine. Astruc made 
a number of experiments on the effect of decolorizing by 
means of various forms of charcoal, including crude and puri- 
fied bone-black, lamp-blacks, and vegetable charcoal. All 
the decolorizers absorbed a little alcohol (0.4 to 1.5 per cent, 
of a total of 7.8); a small proportion of the total acidity; 0.5 
to 2.65 per cent, of the glycerol (out of a total of 4.5 per cent.); 
and 0.95 to 2.65 per cent, out of a total of 3.45 per cent, of tannin, 
besides extracting the coloring-matter. The crude bone-blacks 
arc distinguished from the purified blacks and vegetable char- 
coals by the fact that the former remove almost the whole of 
the tartrates and a larger proportion of glycerol, and double 
the proportion of mineral matter in solution, the increase being 



WINE 351 

entirely in soluble ash constituents (chiefly calcium phosphates), 
whereas the soluble portion is diminished. The decolorizing 
power of the vegetable blacks is low and a much larger quantity 
is required, the effect of which on the chemical constitution is 
greater than that of a suitable amount of bone-black. 

The following is an analysis by Hougounenq of a white 
wine supposed to have been prepared from red wine by the 
addition of potassium permanganate and charcoal: 

Alcohol, 7.13 per cent. 

Extract (in vacuo), 22.27 grams per liter. 

Ash, 3.59 

Alkalinity of ash as potassium carbonate,. 1.16 

Potassium sulfate, 1.14 

Acidity, total, as sulfuric acid, 4.25 

" volatile, as acetic acid, 1.23 

Reducing substances as glucose, 1.47 

Glycerol, i .07 

The ash was red and porous. The sample contained 0.59 
gram of manganous oxid per liter. 

Analyses of pure Ohio wines by Smith & Parks are of interest 
as indicating a composition in some respects different from 
European wines. The average of solids is slightly lower than 
that of foreign wines, but the most important differences are 
the percentages of glycerol and ash. Published reports from 
European samples give ash usually above o.i per cent., and from 
0.5 to 0.8 per cent, of glycerol, while the maximum and mini- 
mum found with the Ohio samples are 0.15 to o.io for ash, and 
0.95 and 0.29 for glycerol. Since these two constituents, to- 
gether with the solids, are of much value in determining the 
genuineness and purity of a sample of wine, the differences are 
most important. Many authorities state that in the natural 
process of alcoholic fermentation, glycerol and alcohol are pro- 
duced in the ratio of from 7 to 14 parts of the former to 100 
parts of the latter, from which would be drawn the inference, 
when this maximum is exceeded, that glycerol has been added ; 



352 FOOD ANALYSIS 

while in case the ratio of glycerol to alcohol is below 7 : 100, 
the inference would be drawn that the sample has been fortified 
by the addition of alcohol. Such conclusions in the case of 
Ohio wines would be quite misleading. Smith & Parks also 
call attention to the fact that care must be exercised, when 
these wines are under consideration, in drawing conclusions 
as to the addition of water from the fact of low ash and solids. 
Appreciable amounts of copper, zinc, lead, and arsenic are 
occasionally found in wine. These are probably introduced 
along with crude glucose, anilin colors, or other materials w^hich 
have been added. Lead has been introduced by the use of 
bottles that have been cleaned with shot. 

Analytic Methods. 

For the detection of alcohol when present in very small amount 
several tests have been devised, but the reactions are produced 
by other substances. The following are the most satisfactory. 
They should be applied to samples containing no active in- 
gredients but water and alcohol; ordinary mixtures should, 
therefore, be distilled and the distillate tested. 

Hardy's Test. — A small quantity of powdered guaiacum 
resin taken from the interior of a lump is shaken with a few 
c.c. of the sample, the liquid filtered, and a few drops of hy- 
drogen cyanid solution and a drop of very dilute copper sul- 
fate solution added. In the presence of alcohol a blue tint 
much deeper than that due to the copper sulfate will appear. 

Merck's Modification 0} Davy's Test. — Pure molybdenum 
trioxid is dissolved in warm sulfuric acid, and the mixture 
poured through the solution to be tested, keeping the mass as 
near as possible at 60°. Alcohol produces a blue ring at the 
junction of the liquids. 

Hager's Modification oj Lichen's Test. — 10 c.c. of the sample 
are mixed with 5 drops of a 10 per cent, solution of sodium 
hydroxid and the liquid heated to about 50°. Potassium 



WINE 353 

iodid-iodin solution is added drop by drop with shaking until 
the liquid is permanently yellowish-brown. It is then de- 
colorized by the cautious addition of more sodium hydroxid. 
If alcohol is present, iodoform will be produced as a yellow 
precipitate of characteristic odor and crystalline form. Under 
rather high magnifying power (200 diameters) these are seen 
to consist of hexagonal plates or six-pointed stars. This is a 
good test, but requires care. The iodin solution should be 
strong and the directions should be followed closely. The re- 
action is given by many bodies, but not by methyl alcohol, fusel 
oil, common ether, chloral, chloroform, or glycerol. 
Determination of Alcohol. 

Specific gravity determinations of commercial liquors are 
made, but the figures have little practical bearing. 

Alcohol may be determined directly in spirits and other mix- 
tures containing but little solid matter by taking the specific 
gravity and correcting for temperature. This is the method 
used by revenue officers. 

For determining the alcohol in samples containing appre- 
ciable amounts of solid matters, several methods have been 
devised, of which only two deserve mention here: distilla- 
tion and observation of boiling-point. 

For distillation 200 c.c. of the sample should be taken, 100 
c.c. of water added, the mixture distilled until 200 c.c. are 
collected. The specific gravity of this is taken at standard 
temperature and the percentage of alcohol ascertained by the 
annexed tables. 

The tables here given are condensed from those recalculated 
by Edgar Richards from the determinations of Gilpin, Drink- 
water and Squibb, and published by the A. O. A. C. All data 
are given at '^■^° . The figures in columns designated volume 
(V) or weight (W) arc the percentage of absolute alcohol, by 
volume or weight respectively, corresponding to the specihc 
gravity indicated. When the percentage in two lines is the 
31 



354 



FOOD ANALYSIS 



Speci- 






Speci- 






Speci- 






Speci- 






fic 


Vol- 


Weight 


fic 


Vol- 


Weigiii 


fic 


Vol 


Weight 


fic 


VOL- 


Wkight 


Grav- 


ume. 




(iKAV- 


ume 




Grav- 


ume. 




Grav- 


UMF. 




ity. 






nv. 






ity. 






ity. 






I.OOOO 


0.0 


0.0 


0.9928 


50 


4.0 


0.9866 


10. 


8.0 


0.9811 


150 


12. 1 


o.gggS 


1 





20 


I 





64 


I 


I 


10 


I 


2 


96 


2 


I 


25 


2 


I 


63 


2 


2 


09 


2 


2 


95 


3 


2 


24 


3 


2 


62 


3 


2 


08 


3 


3 


93 


4 


1 


22 


4 


3 


61 


4 


3 


07 


A 


4 


0.9992 


0.5 


0.4 


0.9921 


5-5 


4.4 


0.9860 


10 5 


8.4 


0.9806 


15.5 


12.5 


90 


6 


4 


20 


6 


4 


59 


6 


5 


c5 


(; 


6 


89 


7 


5 


18 


7 


5 


58 


7 


6 


04 


7 


7 


87 


8 


6 


n 


8 


6 


56 


8 


7 


03 


8 


7 


86 


9 


7 


16 


Q 


7 


55 


9 


9 


02 


9 


8 


0.9984 


I.O 


0.7 


0.9914 


6.0 


4.8 


0.9854 


II. 


8.8 


0.9801 


16.0 


12.9 


«3 


I 


8 


13 


I 


8 


53 


I 


9 


GO 


I 


130 


81 


2 


9 


12 


2 


9 


52 


2 


90 


0.9799 


2 


I 


80 




10 


II 


3 


50 


5' 


3 


I 


98 


n 
J 


2 


79 


4 


I 


09 


4 


I 


50 


4 


I 


97 


4 


2 


0.9977 


1-5 


I.I 


0.9908 


65 


5-2 


0.9849 


"•5 


9.2 


0.9796 


16.5 


133 


76 


6 


2 


07 


6 


2 


47 


6 


:> 


95 


6 


4 


74 


7 


3 


05 


7 


3 


46 


7 


4 


94 


7 


5 


73 


8 


4 


04 


8 


4 


45 


S 


5 


92 


8 


6 


71 


9 


5 


03 


9 


5 


44 


9 


5 


91 


9 


7 


0.9970 


2.0 


1-5 


0.9902 


7.0 


5-6 


0.9843 


12.0 


9.6 


0.9790 


17.0 


13.7 


68 


1 


6 


00 


I 


6 


42 


1 


7 


89 


I 


8 


67 


2 


7 


9899 


2 


7 


41 


2 


8 


88 


2 


9 


65 


3 


8 


98 


3 


8 


40 


3 


9 


87 


3 


140 


64 


4 


9 


97 


4 


9 


39 


4 


lO.O 


86 


4 


I 


0.9962 


2.5 


1.9 


0.9895 


7-5 


6.0 


0.9838 


12.5 


10. 


09785 


17-5 


14. 1 


61 


6 


2.0 


94 


6 


I 


37 


6 


I 


84 


6 


2 


60 


7 


I 


93 


7 


I 


35 


7 


2 


83 


7 


3 


58 


8 


2 


92 


8 


2 


34 


8 


-> 




82 


8 


4 


57 


9 


-1 



90 


9 


3 


33 


9 


4 


81 


9 


5 


0.9955 


30 


2-3 


0.9889 


8.0 


6.4 


0.9832 


13.0 


10.4 


0.9780 


18.0 


14 6 


54 


I 


4 


88 


I 


5 


31 


I 


5 


79 


I 


6 


52 


2 


5 


87 


2 


5 


30 


2 


6 


78 


2 


7 


51 


3 


6 


86 


3 


6 


29 


3 


7 


77 


3 


8 


50 


4 


7 


84 


4 


7 


28 


4 


8 


76 


4 


9 


0.9948 


3-5 


2.8 


0.9883 


8.5 


6.8 


6.9827 


13 5 


10.9 


9775 


18.5 


15.0 


47 


6 


8 


82 


6 


9 


26 


6 


9 


74 


6 


^ 


45 


7 


9 


81 


7 


9 


25 


7 


II. 


73 


7 


I 


44 


8 


30 


80 


8 


7.0 


24 


8 


I 


72 


8 


2 


43 


9 


I 


78 


9 


I 


23 


9 


2 


71 


9 


3 


0.9941 


4.0 


3-2 


0.9877 


9.0 


7.2 


0.9821 


14.0 


"•3 


9770 


19 


154 


40 


I 


2 


76 


I 


3 


20 


I 


3 


69 


I 


5 


39 


2 


3 


75 


2 


3 


19 


2 


4 


68 


2 


5 


37 


3 


4 


74 


3 


4 


18 


3 


5 


67 


3 


6 


36 


4 


5 


73 


4 


5 


17 


4 


6 


66 


4 


7 


0.9934 


4-5 


3-6 


0.9871 


9-5 


7.6 


0.9816 


14-5 


11.7 


0.9765 


19 5 


15.8 


33 


6 


6 


70 


6 


7 


i> 


6 


8 


64 


6 


9 


32 


7 


7 


69 


7 


8 


14 


7 


8 


63 


7 


16.0 


30 


8 


8 


68 


8 


8 


13 


8 


9 


62 


8 





29 


9 


9 


67 


9 


9 


12 


9 


12.0 


61 


9 


I 



WINE 



355 



S. G. 


V. 


w. 


S. G. 


V. 


w. 


S. G. 


V. 


w. 


S. G. V. 

1 
1 

1 


W. 


0.9760 


20.0 


16.2 


0.9709 


25.0 


20.4 


0.9654 


30.0 


24.6 


0.9591 35.0 


28.9 


59 


I 


3 


08 


I 


5 


52 


I 


7 


89 I 


29 


58 


2 


4 


07 


2 


6 


51 


2 


8 


88 2 


I 


57 


3 


5 


06 


3 


6 


50 


3 


9 


86 3 


2 


56 


4 


5 


05 


4 


7 


49 


A 


250 


85 4 


3 


0.9755 


20.5 


16.6 


0.9704 


255 


20.8 


0.9648 


30.5 


25.0 


0.958435-5 


293 


54 


6 


7 


03 


6 


9 


46 


6 


I 


82 


6 


4 


53 


7 


8 


02 


7 


21.0 


45 


7 


2 


81 


7 


5 


52 


8 


9 


01 


8 


I 


44 


8 


o 
J 


80 


8 


6 


51 


9 


17.0 


00 


9 


I 


43 


9 


4 


78 


9 


■ 7 


0.9750 


21.0 


17.0 


0.9699 


26.0 


21.2 


0.9642 


31.0 


255 


0.9577 


36.0 


29.8 


49 


I 


I 


98 


I 


3 


40 


I 


6 


75 


I 


9 


48 


2 


2 


96 


2 


4 


39 


2 


6 


74 


2 


30.0 


47 


3 


3 


95 


3 


5 


38 


3 


7 


73 








46 


4 


4 


94 


4 


6 


37 


4 


8 


71 


4 


I 


0-9745 


21.5 


17-5 


0.9693 


26.5 


21.6 


0.9636 


31-5 


25.9 


0.9570 


36.5 


30.2 


44 


6 


5 


92 


6 


7 


34 


6 


26.0 


68 


6 


3 


43 


7 


6 


91 


7 


8 


33 


7 


I 


67 


7 


4 


42 


8 


7 


90 


8 


9 


32 


8 


2 


66 


8 


5 


41 


9 


8 


89 


9 


22 


31 


9 


2 


64 


9 


6 


0.9740 


22.0 


17.9 


0.9688 


27.0 


22.1 


0.9629 


32.0 


26.3 


09563 


37 -o 


30.7 


39 


I 


18.0 


87 


I 


2 


28 


I 


4 


61 


I 


7 


38 


2 





86 


2 


2 


27 


2 


5 


60 


2 


8 


37 


3 


I 


85 


3 


3 


26 


3 


6 


58 


3 


9 


36 


4 


2 


83 


4 


4 


24 


4 


7 


57 


4 


31 


0.9735 


22.5 


18.3 


0.9682 


27-5 


22.5 


0.9623 


32.5 


26.8 


0.9556 


37-5 


3I-I 


34 


6 


4 


81 


6 


6 


22 


6 


8 


54 


6 


2 


33 


7 


5 


80 


7 


7 


21 


7 


9 


53 


7 


3 


32 


8 


5 


79 


8 


7 


19 


8 


27.0 


51 


8 


4 


31 


9 


6 


78 


9 


8 


18 


9 


I 


50 


9 


4 


0.9730 


23.0 


18.7 


0.9677 


28.0 


22.9 


0.9617 


33 


27.2 


0.9548 


38.0 


31-5 


29 


I 


8 


76 


I 


23.0 


15 


I 


3 


47 


I 


6 


28 


2 


9 


74 


2 


I 


14 


2 


4 


45 


2 


7 


27 


3 


19.0 


73 


3 


2 


13 


3 


4 


44 


3 


8 


26 


4 





72 


4 


3 


12 


4 


5 


42 


4 


9 


0.9725 


235 


19. 1 


0.9671 


28.5 


233 


0.9610 


33-5 


27.6 


0.9541 


38.5 


32.0 


24 


6 


2 


70 


6 


4 


09, 


6 


7 


39 


6 


I 


23 


7 


3 


69 


7 


5 


o8| 


7 


8 


3^ 


7 


2 


22 


8 


4 


68 


8 


6 


06 


8 


9 


36 


8 


2 


21 


9' 


5 


66 


9 


7 


c5 


9 


280 


35 


9 


-* 

J 


0.9720 


24.0 


19-5 


0.9665 


29.0 


238 


9604 


340 


28.0 


0.9533 


390 


32.4 


19 


I 


6 


64 


I 


8 


03 


I, 


I 


32 


I 


5 


18 


2i 


7 


63 


2 


9 


01 


2| 


2 


30 


2 


6 


17 


3 


8 


62 


3 


24.0 


oo 






J 


29 




7 


15 


4 


9 


61 


4 


I 


0.9599 


4 


4 


27 


4 


8 


9.9714 


245 


20.0 


0.9660 


29-5; 


24.2 


0.9597 


34-5 


28.5 


0.9526 


39-5 


32.9 


13 


6 





58 


6 


3 


96 


6 


6 


24 


^1 


9 


12 


7i 


I 


57 


7 


4 


95 


7 


7 


23 


7! 





II 


8 


2 


56 


8, 


4 


93, 


8 


7 


21 


8 

1 


I 


ID 


9 


3 


55| 


9 


5 


92 

1 


9 

1 


8 


20 


9 

1 


2 



o: 



^6 



FOOD ANALYSIS 



S. G. V. 


33-3 


S.G. 


V. 


W. 


S.G. 


V. 


W. 


S.G. 


V. 


W. 


0.9518 40.0 


0.9478 


42.5 


35-5 


0.943645.0 


37-8 


0.9391 


47-5 


40.1 


16 


I 


4 


77 


6 


6 


34 


I 


9 


89 


6 


2 


15 


2 


5 


75 


7 


7 


32 


2 


38.0 


87 


7 


3 


13 


3 


6 


73 


8 


8 


31 


3 


I 


86 


8 


4 


12 


4 


7 


72 


9 


9 


29 


4 


2 


84 


9 


5 


0.9510 


40.5 


33-7 


0.9470 


43 


36.0 


0.9427 


45-5 


38.3 


0.9382 


48.0 


40.6 


09 


6 


8 


68 


I 


I 


25 


6 


3 


80 


I 


6 


07 


7 


9 


67 


2 


2 


24 


7 


4 


78 


2 


7 


05 


8 


340 


65 


3 


3 


22 


8 


5 


76 


■^ 

J 


8 


04 


9 


I 


63 


4 


3 


20 


9 


6 


74 


4 


9 


0.9502 


41.0 


34-2 


0.9462 


43-5 


36.4 


0.9418 


46.0 


38.7 


09373 


48.5 


41.0 


01 


I 


3 


60 


6 


5 


17 


I 


8 


71 


6 


I 


0.9499 


2 


4 


58 


7 


6 


15 


2 


9 


69 


7 


2 


98 


3 


5 


57 


8 


7 


13 


3 


390 


67 


8 


3 


96 


4 


5 


55 


9 


8 


1 1 


4 


I 


65 


9 


4 


0.9494 


41-5 


34-6 


0.9453 


44 


36.9 


0.9409 


46.5 


39-2 


0.9363 


49.0 


41-5 


93 


6 


7 


51 


I 


370 


08 


6 


3 


61 


I 


6 


91 


7 


8 


50 


2 


I 


06 


7 


3 


59 


2 


7 


90 


8 


9 


48 


3 


2 


04 


8 


4 


57 


3 


8 


88 


9 


350 


46 


4 


3 


02 


9 


5 


55 


4 


9 


0.9486 


42.0 


35-1 


0.9445 


44-5 


37-3 


0.9400 


470 


396 


0.9354 


49 5 


41.9 


85 


I 


2 


43 


6 


4 


09399 


I 


7 


52 


6 


42.0 


83 


2 


3 


41 


7 


5 


97 


2 


8 


50 


7 


1 


81 


3 


4 


39 


8 


6 


95 


3 


9 


48 


8 


2 


80 


4 


4 


38 


^ 


7 


93 


4 


40.0 


46 


9 


3 



same, the actual difference is in the second decimal place, 
which has been omitted in this condensed table. 

Alcohol may be determined by noting the temperature of 
the vapor from the boiling liquid. Wiley has described a form 
of apparatus (Fig. 53) for this purpose. It consists of the flask, 
F, which is closed by the rubber stopper, carr}'ing the large 
thermometer, B, and a tube leading to the condenser, D. The 
vapors which are given off during ebullition are condensed in 
D and return to the flask through the tube, as indicated in the 
figure, entering the flask below the surface of the liquid. 

The flask is heated by a gas-lamp and is placed upon a per- 
forated disk of asbestos in such a way as to entirely cover the 
hole in the center of the asbestos disk, which is a little smaller 
than the bottom of the flask. The whole apparatus is protected 
from external influences of temperature by the glass cylinder, 



WINE 



357 



E, which rests upon the asbestos disk below and is covered with 
a detachable, stiff rubber-cloth disk above. 

The thermometer, C, indicates the temperature of the air 
between F and E. The 
reading of the thermome- 
ter, B, should always be 
made at a given tempera- 
ture of this surrounding 
air. The tube leading 
from the condenser, D, to 
the left is made long and 
is left open at its lower 
extremity in order to 
maintain atmospheric 
pressure in F and at the 
same time prevent the 
diffusion of the alcoholic 
vapors through D. 

The flame of the lamp 
is so regulated as to bring 
the temperature indicated 
by the thermometer C to 
about 90° in ten minutes, 
for substances containing 
not over 5 per cent, of 
alcohol. After boiling for 
a few minutes, the tem- 
perature, as indicated in 
the thermometer B, is con- 
stant, and the readings of 
the thermometer should be made at intervals of about half a 
minute, for ten minutes. Some pieces of scrap platinum placed 
in the flask will prevent bumping and secure a more uniform 
evolution of vapor. Slight variations, due to the changes 




Fig. 53. 



358 FOOD ANALYSIS 

in temperature of the vapors, are thus reduced to a minimum 
efifect upon the fmal resuUs. The apparatus is easily oper- 
ated, is quickly charged and discharged, and with it at least 
three determinations of alcohol can be made in an hour. 

The thermometer used is the same that is employed for the 
freezing and boiling points in the determination of molecular 
weights. The reading of the thermometer is arbitrary, but 
the degrees indicated are centigrade. The thermometer is set 
in the first place by putting the bulb in water containing 16 
grams of common salt to 100 c.c; when the water is fully 
boiling, the excess of mercury is removed from the column in 
the receptacle at the top, and then, on placing in boiling water, 
the column of mercury will be found a little above the 5° mark. 
This will allow a variation in all of 5° in the temperature, and 
a thermometer thus set can be used for the estimation of per- 
centages of alcohol from one to five and a half, by volume. 
When the liquor contains a larger percentage of alcohol than 
this, it is advisable to dilute it until it reaches the limit. 

In order to avoid frequent checking of the thermometer, 
rendered necessary by changes in barometric pressure, a second 
apparatus, made exactly like the one described, is used, in 
which water is kept constantly boiling. It is only necessary, 
in this case, to read the two thermometers at the same instant, 
in order to make the necessary correction required by changes 
in barometric pressure. 

Each 0.8° corresponds to about i per cent, by volume of 
alcohol in liquors containing not more than 5.5 per cent. For 
example, if, in a given case, the temperature of the vapor of 
boiling water, as marked by the thermometer, is 5.155° and 
the temperature of that from a sample of beer is 2.345°, the 
difference is equivalent to 2.810°, and the percentage of alcohol 
by volume is, therefore, 2.81 divided by 0.80 = 3-5 1- 

The thermometer used is graduated to hundredths of a 
degree, and may be read by a cathetometer to 0.005°. I^ niay 



WINE 359 

be protected and its readings facilitated by immersing the bulb in 
a test-tube containing water. 

£^/rac/ is determined as indicated on page 27. When the 
amount exceeds 6 per cent., it will be best to dilute the sample 
with an equal volume of water, making allowance for this in 
calculating results. Some operators advise the use of 50 c.c. 
for this determination, but good results can be obtained in 
small dishes with 5 c.c. 

Ash. — The residue from the extract determination is incin- 
erated at as low a heat as possible. Repeated moistening, 
drying, and heating to redness are advisable to get rid of 
carbon. 

Gum and Dextrin (in \\dne). — 4 c.c. of the sample are mixed 
with 10 c.c. of 96 per cent, alcohol. If gum arabic or dextrin 
is present, a lumpy, thick, and stringy precipitate is produced; 
pure wine becomes at first opalescent and then gives a flocculent 
precipitate. 

Total Acidity. — Any carbonic acid present is removed by 
shaking a portion of the sample; 25 c.c. are transferred to a 
beaker and, with white wines, 10 drops of azolitmin solution 
added. Decinormal sodium hydroxid solution is added until 
the red color changes to blue. The result is expressed in terms 
of tartaric acid, i c.c. of l^ alkali equals 0.0075 gram tartaric 
acid. 

Determination of Volatile Acids. — 50 c.c. of wine to which a 
little tannin has been added, to prevent foaming, are distilled 
in a current of steam. The flask is heated until the liquid 
boils, the lamp turned down, and the steam passed through 
until 200 c.c. have been collected in the receiver. The dis- 
tillate is titrated with ^^ sodium hydroxid solution, and the 

result expressed as acetic acid: i c.c. - sodium hydroxid 
solution equals 0.006 gram acetic acid. 

Total Sulfites. — 25 c.c. of normal potassium hydroxid arc 



o 



60 FOOD ANALYSIS. 



placed in a 200 c.c. flask, 50 c.c. of the sample added, best 
by means of a pipet, the liquids mixed and allowed to stand 
15 minutes with occasional shaking. 10 c.c. of dilute (25 
per cent), sulfuric acid are added, with 3 c.c. of starch solution, 

and the mixture titrated with ^ iodin solution introduced as 

50 

rapidly as possible. The numVjer of c.c. of iodin required to 
secure a blue color lasting for some minutes, multiplied by 
0.00128, will give the equivalent of sulfur dioxid in grams per 
100 c.c. 

Sidjuroiis Acid. — 50 c.c. of the sample are mixed in a 200 c.c. 
flask with 5 c.c. of dilute sulfuric acid (i : 3), a small piece of 
sodium carbonate added to expel air and the solution titrated 
with ^ iodin solution as directed above. The c.c. of solution 

so 

required multiplied by 0.00128 gives the weight of sulfur dioxid 
in grams per 100 c.c. of sample. 

A sample of Bordeaux wine, examined in 1904 by the U. S. 
Customs authorities, was refused admission on the ground of 
excessive content of sulfur dioxid and sulfites. The sample 
gave the following results, which accord closely with those 
reported by the official analyst. 

Total sulfur dioxid, 0.070 per 100 c.c. 

Sulfurous acid (calculated as sulfur dioxid),. . . .0.045 " 

Glycerol. — loo c.c. of wine are evaporated in a porcelain 
dish to about lo c.c, i gram of quartz sand and 2 grams of 
milk of lime containing 40 per cent, calcium hydroxid added, 
and the evaporation cautiously carried almost to dryness. The 
residue is mixed with 50 c.c. of alcohol, 90 per cent, by weight, 
using a glass pestle or spatula to break up any solid particles, 
heated just to boiling on the water-bath, allowed to settle, 
and the liquid filtered into a flask graduated at 100 and no c.c. 
The residue is repeatedly extracted in a similar manner with 
10 c.c. portions of hot alcohol. The contents of the flask are 
cooled to 15°, diluted with alcohol to the 100 c.c. mark, and 



WINE 361 

filtered rapidly. 50 c.c. of tlie filtrate' are evaporated to a sirup 
in a porcelain dish on hot, but not boiling water, the residue 
transferred to a small glass-stoppered graduated cylinder, 
with the aid of 20 c.c. absolute alcohol, and three portions of 
20 c.c. of pure ether added, shaking well between each addition. 
The mixture is allowed to stand until clear, decanted through 
a filter, the cylinder washed at least three times with a mix- 
ture of I part absolute alcohol and 1.5 parts of pure ether, 
the washings being added to the filtrate. The latter is evapo- 
rated to a sirup, dried for one hour at 100°, and weighed. The 
weight doubled gives the grams of glycerol per 100 c.c. of sample. 

Added Colors: see pages 64 to 75. 

.Saccharin. — A substance capable of simulating a saccharin 
reaction by the method given on page 81 often occurs in wine. 
The elimination of the fallacy has been specially studied by 
Chace,^^ who suggests the following method: 

50 c.c. of the sample are extracted with ether in the usual 
way, the residue dissolved in water and extracted with pe- 
troleum spirit. This is evaporated, a small portion tested for 
salicylic acid, and then, whether found or not, the remainder 
of the residue is returned to the liquid from which it was ex- 
tracted. The mixture is made up to 10 c.c, i c.c. of dilute sul- 
furic acid (i .'3) and an excess of 5 per cent, solution of po- 
tassium permanganate added, and the liquid brought to boiling. 
If salicylic acid was shown in the test of the petroleum spirit 
extraction, the solution is boiled for one minute; but if not, this 
length of boiling is unnecessary. While the solution is still hot, 
a small piece of sodium hydroxid is added (sufficient to render 
the liquid alkaline), and after a few minutes the iron and man- 
ganese hydroxids are filtered off, the liquid evaporated to dry- 
ness in a silver or nickel dish, and heated to 2io°-2i5° for 20 
minutes. The residue is dissolved in water, acidified with dilute 
sulfuric acid, extracted with ether or other suitable solvent and 
tested for salicylic acid. If the reaction occurs, saccharin was 
present in the sample. 
32 



362 FOOD ANALYSIS 

Salicylic Acid. The tannin in many articles may mask 
or simulate faint reactions for salicylic acid with ferric salts. 
Alcohol also may interfere. Harr\' & Mummery'^ recommend 
a method for avoiding this: 100 c.c. of the sample are rendered 
faintly alkaline with sodium hydro xid, and concentrated at 
a temperature just below the boiling, until most of the alcohol 
is removed. The liquid is made up to nearly the original 
volume and placed in a flask marked at 300 c.c, 20 c.c. of 
a saturated solution of lead subacetate are added, and the 
solution made alkaline by 25 c.c. of normal sodium hydroxid. 
Tannins are thrown down; lead salicylate passes into the 
alkahne solution. Some albuminous and pectinous bodies 
may also be dissolved; these are reprecipitated by adding 
20 c.c. of normal hydrochloric acid solution. The mass is 
made up to the mark with water, shaken, filtered through a 
dry filter, 200 c.c. of the filtrate collected and acidified dis- 
tinctly, but not excessively, with hydrochloric acid. The 
liquid is refiltered, if necessar}-, and extracted with the immis- 
cible solvent as usual. 

The method is appHcable to many articles. Among other 
advantages it prevents the formation of an emulsion with the 
immiscible solvent. For semisolid materials such as jams 
and jelHes 50 grams should be crushed and mixed with a httle 
water before adding the lead solution. 

Harry & Mummery use three successive extractions with 
ether, and then make a quantitative analysis by evaporating 
the ether, dissolving the residue in dilute alcohol, making up 
to 100 c.c. and comparing the color produced with ferric chlorid 
with that produced by a similar solution of known strength. 

Caramel and Prune Juice. — An extraction method for de- 
tecting these spirits has been devised by Crampton & Simons": 

50 c.c. of the sample are evaporated on the water-bath nearly 
to dryness, the residue washed into a 50 c.c. flask, 25 c.c. of 
absolute alcohol added, and the solution, after cooling to stan- 




WINE 363 

dard temperature, made up to the 50 c.c. mark and mixed. 25 
c.c. are transferred to a separating apparatus and agitated with 
50 c.c. of ether at intervals for about thirty minutes. When the 
layers are separated, the water layer is diluted to 25 c.c, the 
contents of the flask are shaken, and the liquids again allowed 
to separate. The water-layer will be increased slightly, and 
25 c.c. of it should be drawn off for comparison with the 
25 c.c. of solution which has not been treated with 
ether. By comparing the two liquids in a tinto- 
meter, quantitative observations may be made. The 
coloring- matter of oak-wood is soluble in ether, 
and, therefore, spirits not artificially colored become 
lighter when treated by this method. (See also 
page 125.) 

Cramp ton & Simons advise the use of Bramwell's 
modification of Rose's apparatus for the operation. 
It is shown in figure 54. The upper bulb should 
have a capacity of about 150 c.c; the lower bulb 
should have a capacity of 25 c.c, including a por- 
tion of the connecting stem. This stem should have 
a caliber about 4 mm. and it is graduated in 0.02 
c.c from 20 c.c. to 25 c.c, the upper mark only 
being shown in the figure. For diluting the watery 
layer as directed in the process, it is best to attach a 
rubber tube to the lower opening and connect the 
other end of the rubber tube to a flask of water. By 
elevating the flask and controlling the flow of water by Fig. 54. 
the stopcock, any amount of liquid may be introduced. 

Fusel Oil. — Of the many processes devised for this deter- 
mination, the following is selected. It is transcribed as given 
in the Bulletin of the A. O. A. C. The separator (Fig. 54) is 
used; the reagents are: 

Alcohol free jrom jusel oil prepared by fractional distillation 
over sodium hydroxid and diluted so as to contain exactly 




364 FOOD ANALYSIS 

30 per cent, of absolute alcohol by volume (sp. gr., 0.96541 
at 15.6°). 

Anhydrous chlorojorm redistilled. 

Diluted sulfuric acid (sp. gr., 1.2857 at 15.6°). 

Analytic operation: 200 c.c. of the sample are distilled 
until about 25 are left, the flask is allowed to cool, 25 c.c. of 
water added to the contents, and distilled again until the total 
distillate measures 200 c.c. The volume-percentage of this is 
ascertained and it is diluted to 30 per cent, by the rule given 
below. 

To dilute any sample of alcohol to a given percentage mix 
a volumes of the alcohol with sufficient water to make h vol- 
umes of the product, a being the volume-percentage desired 
and b the volume-percentage of the original liquid. Allow 
the mixture to stand until full contraction has occurred and 
the original temperature has been reached and make up any 
deficiency with water. For example, to dilute a distillate 
containing 50 per cent, of alcohol by volume until it contains 
30 per cent., 30 volumes of the 50 per cent, alcohol are mixed 
with enough water to make 50 volumes. 

The special tube and separate flasks containing sufficient of 
the various reagents and the properly diluted distillate are im- 
mersed in water at 15° until all have attained that temperature. 
The tube should have a rubber cap over the lower end to pre- 
vent entrance of water. When the temperature is reached, 
the tube is filled to the 20 c.c. mark with chloroform, drawing 
it through the lower end by suction; then 100 c.c. of the purified 
alcohol are added and i c.c. of the diluted sulfuric acid, the 
apparatus inverted, and shaken vigorously for 3 minutes. The 
stopcock should be opened a couple of times to equalize pres- 
sure. The tube is placed for 15 minutes in water at 15°, turn- 
ing occasionally to hasten the separation of the reagents, and 
then the volume of the chloroform noted. After thoroughly 
cleansing and drying the apparatus, the operation is repeated, 



WINE 365 

using the diluted distillate from the sample under examination, 
in place of the purified alcohol. The increase in the chloroform 
volume with the sample under examination over that v^ith the 
standard alcohol i^ due to fusel oil, and this difference (expressed 
in C.C.), multiplied by 0.663, gives the volume of fusel oil in 
100 C.C., which is equal to the percentage of fusel oil by volume 
in the 30 per cent, distillate. This must be calculated to the 
percentage of fusel oil by volume in the original liquor. 

Gallisin and Foreign Bitters. — For the detection of gallisin, 
indicating the use of commercial glucose, the following method, 
due to Haarstick,''^ is recommended: i liter of the beer is 
evaporated to a thin sirup, and 300 c.c. of 90 per cent, alco- 
hol gradually added in quantities of i to 2 c.c, and finally 95 
per cent, alcohol until the filtrate does not give the slightest 
turbidity on further addition of the latter. The liquid is filtered 
after standing for twelve hours, most of the alcohol distilled 
off, and the remainder evaporated. The residue is dissolved 
in water, diluted to 1000 c.c, and fermented at 20° with well- 
washed beer yeast. After two or three days a little fresh yeast 
is added, and on the fourth day fermentation is complete. 
The concentrated liquor will show no dextrorotation if no gal- 
lisin was present. 

The outline process, given on page 366, for the detection 
of foreign bitter principles in beer is due to Allen^* : 

Methyl Alcohol. — Crude methyl alcohol is sometimes added 
to ethyl alcohol to unfit the latter for use as a beverage. The 
invention of methods by which methyl alcohol can be rectified 
so as to have but slight odor, has led to the adulteration of 
alcohohc beverages and medicines by it. For this, Milliken & 
Scudder^^ devised the following test: 

If the sample be a concentrated spirit, it should be diluted 
three or four times before taking a portion for test. When 
various organic bodies are present, as in malt liquors and 
tinctures, the sample should be distilled and the portion pass- 



366 



FOOD ANALYSIS 



loooc.c. are evaporated half and precipitated boiling with lead acetate, the liquid boiled 
for fifteen minutes and filtered hot. If any precipitate occur on cooling, the liquid is 
again filtered. 



Filtrate. The excess of lead is removed by hydrogen sulfid, and the 
filtered liquid concentrated to about 150 c.c. and tasted. If bitter, the 
liquid is slightly acidulated with dilute sulfuric acid, and shaken re- 
peatedly with chloroform. 



Precipitate i 


contains 


hop- \ 


bitter, c ar a- 


mel- bitter, | 


op he lie 


acid 


(from 


chir- 


etta). p 


h s- 1 


phates. 


albu- 


minous 


mat- 1 


ters, etc 





Chloroform layer, on 
evaporation, leaves a bit- 
ter extract in the case of 
gentian, calumba, quas- 
sia, and old hops (only 
slightly or doubtfully bit- 
ter in the case of chiretta). The residue is 
dissolved in a little alcohol, hot water 
added, and the hot solution treated with 
ammoniacal basic lead acetate and filtered. 



Precipitate contains old 
hops, gentian, and tiaces 
of carawi^/ products. It is 
suspended in water, de- 
composed by hydrogen 
sulfid, and the solution 
agitated with chloroform. 



Chloroform 
LAYER is ex- 
amined by 
special tests 
for gentian 
and old hop- 
bitter. 



Aqueous 

LIQUID 

contains 
traces of 
caramel- 
bitter. 



Filtrate is 
boiled to re- 
move ammo- 
nia, and 
treated with 
a slight ex- 
cess of sul- 
furic acid, fil- 
tered and 
tasted. I f 
bitter, it is 
agitated 
with chloro- 
form, and 
the residue 
examined 
for caluniba 
and quassia. 



Aqueous liquid is shaken with ether. 



Ethereal layer leaves 
a bitter residue in the 
case of chiretta, gen- 
tian, or caluniba. It is 
dissolved in a little al- 
cohol, hot water added, 
and the hot solution 
treated with ammoni- 
acal basic lead acetate 
and filtered. 



P R E C I P I- 

tate is 
treated 
with 
water 
and de- 
composed 
by hydro- 
gen sul- 
fid. The 
filtered 
liquid is 
bitter in 
presence 
of gen- 
tian. 



Filtrate 
is treated 
with a 
slight ex- 
cessof di- 
lute sul- 
furic 

acid, fil- 
tered and 
tasted. 
Bitter- 
ness indi- 
cates cal- 
untba or 
chiretta, 
which 
may be 
re-ex- 
tracted 
with ether 
and fur- 
ther ex- 
amined. 



Aqueous li- 
QU 1 D , if 
still bitter 
is rendered 
alkaline 
and 
shaken 
with ether- 
c hi o r o- 
form. A 
bitter ex- 
tract may 
be due to 
berberin 
(caluniba) 
or strych- 
nin. 



The aqueous 
liquid, 
separated 
from the 
ether-chlo- 
r o f o r m , 
may c on- 
tain cara- 
mel-bitter 
or c hoi in. 



ing 



over between 50° and 100° collected. This distillate 
should give a clear colorless solution when shaken with water. 
In some cases, as when acids or phenolic bodies are present, 
it will be advisable to add sodium hydroxid before distilling. 
A convenient amount of the material to be tested is placed in 
a beaker which is set in a dish of cold water. 

A close spiral of about 2 cm. long is made by winding 
copper wire around a lead-pencil. The metal is superficially 



WINE 367 

oxidized by heating in the upper part of the Bunsen flame, and 
while red-hot plunged into the distilled or diluted sample, 
as noted above. This treatment is repeated at least six 
times, rinsing the wire in cold water between each heating. 
The liquid is then tested by either the phloroglucol or phe- 
nylhydrazin test, as given on page 83. The method will 
detect at least one per cent, of methyl alcohol. If much ethyl 
aldehyde be present in the liquid, it will be of advantage to 
boil the liquid, after the hot wire treatment, in a flask attached 
to an inverted condenser, as ethyl aldehyde evaporates more 
readily under these conditions than formaldehyde. 

It is necessary to prove the absence of formaldehyde before 
making the test. This can generally be done best by the 
phenylhydrazin test. If formaldehyde is present it can be 
wholly removed by adding a moderate excess of potassium 
cyanid, and distilling. The distilled liquid will contain no 
formaldehyde if the cyanid had been added in sufficient amount. 
As the amount of formaldehyde in foods, beverages and tinc- 
tures is small, it will usually be found that i c.c. of a normal 
solution of potassium cyanid will be ample for the purpose. 
After adding the potassium cyanid, a portion of the liquid may be 
at once tested with phenylhydrazin; if no bluish or greenish 
color is produced, the remaining portion of the liquid should 
be at once distilled. A small portion of the distillate should, 
as a precaution, be tested for formaldehyde. 

Borates, present in many pulp fruits, can be detected by 
evaporating about 20 grams of the juice or fruit to dryness, 
burning off and treating the ash by the turmeric test. (See 
page 82.) A proportion of borates, equivalent to i part of 
boric acid to 5000 parts of wine, can be detected by the flame 
test. 50 c.c. of the sample are neutralized with sodium 
hydroxid, evaporated to dryness, charred and the carbon burn 
off somewhat. The residue is cooled, mixed with a little 
sulfuric acid and 2 c.c. of alcohol and liditcd. In a darkened 



3^8 lOOD ANALYSIS 

place, the l)oric acid flame is easily seen. It may be verified 
by the spectroscope. 

The quantitative determination of borates in fruit or juices, 
fermented or unfermented, may be satisfactorily carried out 
by the method of Allen & Tankard.^' 

loo c.c. of the liquid is evaporated to dryness with lo c.c. of a 
lo per cent, solution of calcium chlorid. In the case of solid or 
semisolid materials, the mass should be well broken up and the 
solution of calcium chlorid well mixed with it. The dry mass 
is well charred, boiled with 150 c.c. of water, and the liquid 
filtered. The residue is ashed thoroughly, boiled with a 
second portion of 150 c.c. of water, allowed to stand for 12 
hours, and filtered cold. The filtrates are mixed, evaporated 

to 30 c.c, cooled and neutralized with ^ acid and methyl 

10 

orange. An equal volume of glycerol and a little phenol- 
phthalein solution are added and the liquid titrated 
with J^ sodium hydroxid (free from carbonate). 10 c.c. 
more of glycerol should be added. If the titration is complete, 
the red will remain, i c.c. of the sodium hydroxid solution 
represents 0.00175 boric anhydrid, equivalent to 0.0031 
orthoboric acid. 

Care must be taken that all the boric acid is in solution be- 
fore beginning the titration. Allen & Tankard recommend 
that the residue be extracted with a third portion of 150 c.c. and 
this titrated separately. It should give no boric anhydrid; 
if it does, the amount can be added to the other result. 

The process depending on the volatility of methyl borate 
is more troublesome and not more accurate. 

Bigelow has described the follow^ing approximation method 
for borates: A series of solutions containing amounts of boric 
acid from o.ooi to 0.020 gram in dilute hydrochloric acid (i part 
of strong acid to 15 parts of water) is prepared. A drop of 
each solution is evaporated on a piece of turmeric paper 2 cm. 



WINE 369 

square and the color noted, care being taken that the drops 
are uniform. 50 c.c. of the wine are made sHghtly alkahne 
with calcium hydroxid solution, evaporated to dryness, and 
burned to an ash. 3 c.c. of water are added to the ash and 
then half- strength hydrochloric acid drop by drop until the 
liquid is acid. The solution is then made up to 5 c.c. with 
hydrochloric acid one- sixth the strength of the strong acid, 
the mass mixed, and a drop tested on a piece of turmeric paper 
and compared with the standards. If stronger than a standard 
that is of characteristic tint, the liquid should be diluted with 
I to 15 hydrochloric acid and again tested. 

Sucrol (Dulcin) (Jorisson's method as given by A. O. 
A. C). — 100 c.c. of the sample, if liquid, or a corresponding 
amount of solid or semisolid material, are mixed with 5 grams 
of lead carbonate, evaporated to sirupy consistence and ex- 
tracted several times with 90 per cent, alcohol. The alcohol 
is evaporated to dryness, the residue extracted with ether and 
the ether allowed to evaporate without heat. The residue 
thus obtained is stirred up with 5 c.c. of water, mixed with 
3 c.c. of a 10 per cent, solution of mercuric nitrate and heated 
for 10 minutes on the water-bath. A violet-bluish tint is 
produced if dulcin is present. The tint is changed to deep 
violet by addition of lead dioxid. 

Polarimetric Examination. — In the routine examination of 
wine polarimetric readings are taken directly (after clarifica- 
tion, if necessary). Sweet wines are examined directly, also 
after inversion and fermentation. The following are the direc- 
tions for these processes given by the A. O. A. C. : 

Clarification. — For white wines, 60 c.c. of the sample are 
mixed with 3 c.c. of lead subacetate solution and 3 c.c. of water 
and filtered. (The method of clarification by powdered lead 
subacetate, with removal of the lead by potassium oxalate as 
described on page 118, might be advantageous.) :^t^ c.c. of 
the filtrate arc mixed with 1.5 c.c. of a saturated sohition of 



370 FOOD ANALYSIS 

sodium carbonate and 1.5 c.c. of water, again filtered, and ex- 
amined in the polarimeter. The reading must be multiplied 
by 1.2 to compensate for the dilution. For red wines the same 
amount of sample is taken, and 6 c.c. of lead subacetate solution 
are used without addition of water. 33 c.c. of the filtrate are 
treated with 3 c.c. saturated sodium carbonate solution, filtered, 
and the reading multiplied by 1.2. With sweet wines 100 c.c. are 
mixed with 2 c.c. of lead subacetate solution and 8 c.c. of water 
and filtered. 55 c.c. of the filtrate are mixed with 0.5 c.c. of 
saturated sodium carbonate solution and 4.5 c.c. of water, 
filtered, and the reading multiphed by 1.2; 1,^ c.c. of the filtrate, 
prior to the addition of the sodium carbonate, are mixed with 
3 c.c. of hydrochloric acid and the liquid inverted according to 
the method on page 119. The liquid is cooled quickly, filtered, 
the reading taken at known temperature, and multiplied by 
1.2. 50 c.c. of the sample are freed from alcohol by concen- 
tration, made up to the original volume with water, mixed with 
some well-washed beer yeast, and the mass kept at 30° until 
fermentation is complete, which will usually require from 48 to 
72 hours. The liquid is then transferred to a 100 c.c. flask, a 
few drops of acid mercuric nitrate added (p. 213), then some 
lead subacetate solution, followed by the saturated sodium 
carbonate solution. The flask is filled to the mark, the liquid 
mixed, filtered, and the reading multiplied by 2. 

The polarimetric data obtained in the above examinations 
are interpreted according to the following schedule: 

If the direct examination shows no rotation, the sample may 
nevertheless contain invert-sugar associated with the dextro- 
rotatory unfermentable impurities of glucose or with sucrose. 
If inversion results in a levorotation, sucrose was present. If 
fermentation results in dextrorotation, it shows that invert- 
sugar (or some other levorotatory fermentable carbohydrate) 
and the unfermentable constituents of glucose were present. 
If the inversion or fermentation produces no change, sucrose, 



MALT-EXTRACTS 3 7 1 

unfermentable constituents of glucose, and levorotatory sugars 
are absent. 

If the direct examination shows dextrorotation, sucrose and 
the unfermentable constituents of glucose may be present. 
If after inversion it is levorotatory, sucrose was present; if 
dextrorotatory to more than 2.3 divisions of the sugar scale, 
the unfermentable impurities of glucose were present; if the 
dextrorotation is less than 2.3 divisions and more than 0.9, a 
portion of the original specimen must be submitted to the 
following treatment: 210 c.c. are mixed with i.i gram of 
potassium acetate and evaporated to a thin sirup, which is 
mixed with 200 c.c. of 90 per cent, alcohol, with constant 
stirring, the solution is filtered, the alcohol removed by distil- 
lation until about 5 c.c. remain, the residue is mixed with washed 
bone-black, filtered into a graduated cylinder, and washed 
until the filtrate amounts to 30 c.c. If this filtrate shows a 
dextrorotation of more than 1.5 divisions on the sugar scale, 
the impurities of glucose were present. 

If the direct examination shows levorotation, and this is 
increased by inversion, sucrose and levorotatory sugar were 
present. If the sample after fermentation shows levorotation 
of 3 divisions, it contains only levorotatory sugars. If after 
fermentation it rotates to the right, levorotatory sugars and 
the unfermentable impurities of glucose were present. 

MALT-EXTRACTS 

Some commercial malt-extracts are semi-solid mixtures of 
diastase with products of hydrolysis of starch, such as, maltose, 
dextrose, and dextrin. No alcohol is present; preservatives 
and coloring-matters are not likely to be used. Other extracts 
are dark-colored liquids, containing from 3 to 7 per cent, of 
alcohol, 5 to 15 per cent, of solids, mostly organic, but little, 
if any, active diastase. Preservatives are liable to be used in 
this class, salicylic acid being the most common. 



372 FOOD ANALYSIS 

The usual examination of malt-extracts will involve detec- 
tion of preservatives, determination of alcohol, solid matter, 
and diastatic power. Qualitative tests for diastase may be 
made as follows: 50 c.c. of a solution of 5 grams arrow- 
root starch in 1000 c.c. of water, made as directed below, are 
mixed with about i gram of the extract to be tested, and the 
mixture heated in a water-bath within the limits of 35° and 45°. 
Every few minutes a drop of the liquid is tested on a porcelain 
plate with a drop of iodin solution (page 26), until the blue color 
ceases to appear. It is not worth while to continue the ex- 
periment beyond a half hour, as a malt-extract that will not 
transform the starch in that time is of no diastatic value. The 
solution should not be acid. For quantitative measurement, 
it is necessary to determine the reducing sugar formed in presence 
of a large amount of starch. 10 grams of arrowroot starch are 
stirred into about 100 c.c. of cold water, the mixture added, with 
constant stirring, to 250 c.c. of boiling water, and the boiling 
continued until the starch is well diffused through the mass. 
The solution is diluted to 500 c.c. when cold. 50 c.c. of this 
solution are mixed with 0.5 gram of the sample and the mix- 
ture kept at a temperature between 35° and 45° for half an 
hour. The reducing sugar is measured by the volumetric 
method described on page 113, care being taken that the liquid 
is sufficiently diluted. An experiment without addition of 
starch must be made to determine the amount of reducing 
substance in the extract. 

In some cases rough comparative approximations may be 
made by comparing the color produced by iodin at the end of 
the heating, but the liquid must be largely diluted, and the 
indications are merely suggestive. 

Alcohol and solids are determined as in alcoholic beverages. 



FLESH-FOODS 373 

FLESH-FOODS 

Descriptions of anatomic and histologic characters of flesh- 
foods need not be given here. The following table, from data 
compiled by Allen, will show the principal constituents of some 
meats. The figures are percentages; they must be regarded 
as approximations, as the analytic processes are imperfect. 
The proteid was obtained probably by multiplying the total 
nitrogen — found by the Kjeldahl method — by 6.25 or approxi- 
mate factor. 

Meat from: Water. 

Ox (lean), 76.7 

Ox (fat), 55.4 

Mutton, 76.0 

Mutton (fat), 48.0 

Pig, 72.6 

Horse, 74.3 

Hare, 74.1 

Deer, 75.7 

Chicken, 76.2 

Pigeon, 75.1 

Lobster, 76.6 

Oyster, 80.3 

Herring, 74.6 

Mackerel, 71.2 

Salmon, 64.3 

Cod, 82.2 

Grindley^^ has investigated the action of pure water at a tem- 
perature not over 10° on raw and cooked beef. Some of his 
results are given in the annexed table. The nitrogenous com- 
pounds are in all cases obtained by multiplying the Kjeldahl 
nitrogen by 6.25. 

Cold Water Extract of 
Raw. Boiled. Raw Beef. Boiled Beef. 

Total proteids, 19.96 37-7o - . - . 

Coagulable proteids, 

Albumoses, 

Peptones, 

Meat-bases, 

Acid, (calculated as lactic), . . . 

Ash 



Proteid. 


Fat. 


Ash 


20.7 


1-5 


1.2 


17.I 


26.3 


I.I 


17.1 


5-7 


1-3 


14.8 


36-4 


0.8 


19.9 


6.2 


I.I 


21.6 


2-5 


1.0 


23-3 


i.i 


I.I 


19.7 


1.9 


I.I 


19.7 


1.4 


1-3 


22.1 


I.O 


1.0 


19.I 


I.I 


I.I 


14.I 


i-S 


2.7 


14.S 


9.0 


1-7 


19.4 


8.0 


1-3 


21.6 


12.7 


1-3 


16.2 


0-3 


1-3 



2.18 


0.05 


0.08 


0.12 


0.03 


O.IO 


1.05 


0.87 


1.09 


1. 14 


1. 14 


0.85 



374 FOOD ANALYSIS 

The higher proteid content of boiled beef was due largely 
to the lower proportion of water. 

Grindley found that after extraction of raw meat with pure, 
cold water, a lo per cent, solution of sodium chlorid will ex- 
tract much additional matter, largely coagulable proteids. 
Very little proteid matter is extracted from boiled beef by pure 
water or sodium chlorid solution. 

Adulteration. — Meats are not adulterated in the sense in 
which that word is commonly used, but cheap meats are sub- 
stituted for dear (e. g., horse meat in sausages and mince- 
meat), the meat of diseased and immature animals is often 
sold, preservatives are employed, and applications made to 
improve color or texture. The detection of entozoa is a matter 
of importance. Tests for incipient and actual decomposition 
may be required. 

Analytic Methods. 

Water. — 5 grams of the finely divided material are dried 
according to the methods described on pages 27-32, Parson's 
method being especially worth trial in this connection. 

Ash. — The dry residue obtained in the water determina- 
tion is incinerated according to the methods given on pages 

39 to 41. 

Total Nitrogen. — The Kjeldahl- Gunning process is em- 
ployed. The nitrogen, mulitplied by 6.25, will give an ap- 
proximation to the proteids present. If nitrates are present, 
as will be the case with some preserved meats, the modified 
process, page 37, must be used. 

Fat. — Much of the fat in meat samples can be removed by 
mechanical methods, but some adheres obstinately to the 
muscle-tissue, and it is probable that errors have been made 
in this respect, as with condensed milk. It has been suggested 
that the muscle-tissue be digested with pepsin and hydro- 
chloric acid and the fat extracted from the mass. Good re- 
sults have been claimed for the following process: 2 grams 



FLESH-FOODS 375 

of the material are shaken frequently for six hours with 200 
c.c. of ether and 2 c.c. of mercury and the fat determined in 
an aliquot part of the mixture. 

Most investigators use too much material. It is probable 
that results near enough for practical purposes could be ob- 
tained by continuous extraction for some hours of a few grams 
of the material, but care should be taken that the sample rep- 
resents a fair average of the specimen and that it is very finely 
divided without loss of fat. If the fat is to be examined, a 
large amount of it should be extracted by mechanical means, 
and not with solvents, unless there are special reasons to the 
contrary. 

Horseflesh. — The detection of horseflesh is difficult. Many 
processes have been proposed, but they are all open to objec- 
tion. The principal reliance is upon the detection of glycogen, 
which is present in horseflesh in much greater proportion than 
in most other flesh. 

A brief qualitative method may be used for glycogen (Cour- 
ley & Coremons^^) : 

50 grams of the material are boiled for 30 minutes with water, 
strained, and a portion of the filtrate mixed with a few drops 
of potassium iodid-iodin solution (page 26). With a large 
percentage of horse-meat, the glycogen will produce a dark 
brown liquid, destroyed by heating and reappearing on cooling. 
If starch is present, it must be removed, by adding to a portion 
of the filtrate 2 volumes of glacial acetic acid, again filtering 
and testing this filtrate as above. The following quantitative 
method (Pflueger & Nerking^®) is provisionally recommended 
by A. O. A. C. 

50 grams of the finely- macerated meat are digested on the 
water-bath with 200 c.c. of 2 per cent, solution of potassium 
hydroxid, until solution is practically complete. The liquid 
is cooled, diluted to 20 c.c. with water, shaken, filtered through 
a dry filter, and 100 c.c. of the filtrate mixed with 10 grams of 



376 FOOD ANALYSIS 

potassium iodic! and i gram of potassium hydroxid, which 
arc stirred in until dissolved. 50 c.c. of alcohol are added and 
the mixture allowed to stand overnight. The glycogen will 
separate. It is collected by filtration, washed with a solution 
containing i c.c. of a 73 per cent, solution of potassium hy- 
droxid, 10 grams of potassium iodid, 100 c.c. of water and 50 
c.c. of alcohol. The material is then washed with a mixture 
of 2 volumes of alcohol and i of water, containing sodium chlorid 
in the proportion of 0.007 gram per liter, the residue dissolved 
in water the remaining proteids removed by solution of potas- 
sium mercuric iodid. Filter if necessary, add sodium chlorid in 
the proportion 0.002 gram per 100 c.c, precipitate the glycogen 
again by the alcohol-sodium chlorid solution noted above, wash 
with alcohol containing 0.007 gram sodium chlorid per liter, 
then with absolute alcohol, finally with ether, dry to constant 
weight and weigh. 

As control, the glycogen may be hydrolyzed by boiling for 
3 hours with hydrochloric acid diluted with 10 parts of water, 
and the reducing sugar determined as on page 113, multiplying 
the result by 0.9 for glycogen. 

Bremer states that the most definite test for horseflesh is 
the character of the intramuscular fat. For this test, all visible 
fat is removed from a sample, the mass finely minced, and heated 
in water for an hour at 100°. The fat that floats is poured 
off with the water, the flesh washed several times with boiling 
water, dried for twelve hours at 100°, and the material then 
extracted for several hours with petroleum spirit of low boiling- 
point. Part of the fat thus obtained may be set aside for the 
determination of iodin number, but most of it should be sa- 
ponified, the excess of alkali carefully neutralized with acetic 
acid, and any alcohol that may have been used in the saponifi- 
cation removed by evaporation on the water-bath. The glyc- 
erol-soda method would seem to be applicable here. The 
soap is dissolved in water, a hot solution of zinc acetate added 



FLESH-FOODS 377 

in the proportion of i part of the salt to 2 of fat, the precipitate 
washed with hot water and alcohol, pressed between folds of 
filter-paper, and heated with ten times its volume of anhydrous 
ether for thirty minutes under a reflux condenser. The solu- 
tion is cooled, filtered into a separating funnel, mixed with 
dilute hydrochloric acid, the ethereal layer, which contains 
the acids, washed with water, and parts of it filtered into weighed 
flasks, the ether evaporated, and the iodin number determined. 

It is stated that horseflesh always gives a reddish-brown 
tint to the petroleum spirit solution, but bull's flesh also gives 
such a tint. If, however, glycogen has been detected by the 
tests already mentioned, the petroleum spirit solution is reddish- 
brown, the iodin number of the fat exceeds 65 and that of the 
liquid acids, obtained as above, is considerably over 95, the 
presence of horseflesh may be inferred. 

Starch is often added in large amount to sausage, deviled 
meats and similar articles. It may be detected as noted on page 
87, but it must be remembered that it may be used in small 
amount to facilitate mixture, and may occur in spices, and in 
some brands of table-salt. A slight reaction should be dis- 
regarded. 

The determination of starch cannot be carried out by the 
standard reduction methods on account of interference of some 
of the meat-constituents. For approximation the method of 
Ambuhl, with slight modification, is suggested by A. O. A. C.^^ 

2 grams of the sample are thoroughly macerated with 100 
c.c. of water, then boiled for 30 minutes and the liquid made 
up to 200 c.c, mixed, filtered, an aliquot portion taken, tested 
with the potassium iodid-iodin solution (page 26) and the 
color compared with a solution containing a known amount of 
the same kind of starch as that in sample. The last point may 
be determined by microscopic examination. 

Coloring-matter. — Meats are not infrequently colored to 
give them a fresh look or to improve naturally pale samples. 

Z2> 



37^ FOOD ANALYSIS 

Sausage meats are often colored. Carmine and coal-tar colors, 
especially the latter, are often employed. Fuchsin and eosin 
are among these, but Allen states that benzopurpurin is the 
most common. The detection of artificial colors will generally 
be acomplished satisfactorily by the test on page 64. E. Spath 
has found that heating the material for a short time on the 
water-bath with a 5 per cent, solution of sodium salicylate will 
often dissolve out colors not otherwise soluble. Ordinarily, 
water or alcohol will take out sufficient for the wool-test. For 
the detection of carmine, the method of Klinger and Bujard, 
modified by Bremer, may be used : 20 grams of the minced mate- 
rial are heated for several hours with a mixture of equal parts 
of glycerol and w^ater slightly acidulated with tartacic acid. The 
yellow liquid is freed from fat, filtered, and the coloring-matter 
precipitated as a lake by the addition of alum and ammonium 
hydroxid. This is washed, dissolved in a little tartaric acid, 
and examined in the spectroscope. Absorption bands lying 
between the position of b and D of the solar spectrum are 
characteristic of carmine. 

hnprovers and Preservatives. — Mixtures of potassium ni- 
trate, sodium chlorid, and other mineral preservatives with a 
little coloring-matter — the latter almost always a coal-tar color — 
are sold for improving the appearance of meat. Sulfites are 
also used as improvers — acid sodium sulfite being a common 
form — in quantity equivalent to 0.5 to i per cent, calculated 
as sulfur dioxid. Salicylic acid and borates are also used. As 
these are all soluble in cold water, they may be extracted by 
simple maceration, the watery solution being concentrated at 
a low temperature and treated as directed on pages 78 to 85. 
Formaldehyde is not likely to be used in meat on account of 
its hardening action on proteids. 

Chace *^ found aluminum oxyacetate (basic acetate) as 
a preservative in canned sausage in amounts yielding from 
1 1.2 to 31.3 of aluminum oxid to 100 grams of material. The 



FLESH- FOODS 379 

qualitative test is made as follows: 25 grams of the material 
are partially ashed in a platinum vessel, exhausted with hy- 
drochloric acid, sodium hydroxid added in excess, the liquid 
boiled, filtered, the filtrate acidified with hydrochloric acid, 
and ammonium hydroxid added. Aluminum hydroxid and 
aluminum phosphate are thrown down. Aluminum is not 
a constituent of normal flesh in appreciable amount. For 
quantitative methods, the process of Fresenius & Wacken- 
roder is used. (See page 386.) 

Putrefaction. — To detect incipient putrefaction, Ebers pro- 
posed the following test: A rod moistened with a mixture of 
hydrochloric acid i c.c, alcohol 3 c.c, and ether i c.c. is held 
over the suspected material. The formation of fumes of am- 
monium chlorid shows that putrefaction has begun. Care 
must be taken not to mistake the fumes of the hydrochloric 
acid for those of ammonium chlorid. 

Nitrates. — These are generally in the form of added potas- 
sium nitrate and may be determined by the following method, 
which so far as the preparation of the sample is concerned is 
due to Given. ^^ The operation must be preceded by a deter- 
mination of the chlorids present, as these interfere with the 
process. This can easily be done by titrating in the usual 
manner a cold water solution of the finely divided meat, i 
gram in 200 c.c. will be convenient 

For nitrates, i gram of the sample is placed in a 100 c.c. 
flask, 50 c.c. of water added, and the mixture kept in hot water 
for 20 minutes, with occasional shaking. For each i per cent, 
of sodium chlorid present, 3 c.c. of a saturated solution of 
silver sulfate are added, then 10 c.c. of lead subacetate and 5 
c.c. of alumina-cream, shaking after each addition. The liquid 
is made up to 100 c.c, shaken, filtered through a plaited, dry, 
filter, the filtrate being returned until it is clear. 20 c.c. of the fil- 
trate arc evaporated on the water-bath in a shallow porcelain 
dish to dryness and mixed with i c.c. of the phenoldisulfonic 



380 FOOD ANALYSIS 

acid described below, the acid being stirred over the whole dish 
with a ghiss rod so as to touch all parts of the residue. Heat 
is not needed. The liqurd is diluted with water, rinsed into a 
nesslerizing glass, the dish rinsed several times, these rinsings 
being added to the first, and then ammonium hydroxid or 
sodium hydroxid is added to distinct alkaline reaction. 

The nitrates form picric acid, the alkali forms a picrate; 
the depth of color of this is proportional to the amount present. 
The determination is made by comparing the color with that 
produced by a solution of potassium nitrate of known strength 
treated in the same manner, that is, evaporation on water-bath, 
admixture with i c.c. of the phenoldisulfonic acid, and addition 
of alkali. 

The phenoldisulphonic acid is prepared as follows: 37 
grams of pure sulfuric acid and 3 grams of pure phenol are 
heated for six hours in a flask immersed in boiling water. The 
reagent may crystallize on cooling, but can be easily liquefied 
by gentle warming. 

The nitrate solution for comparison may be made by dis- 
solving o.ioo gram of pure dry potassium nitrate in water to 
make 100 c.c. i c.c. of this is evaporated in a porcelain dish 
on the water bath, the residue mixed with i c.c. of phenol- 
disulfonic acid, stirred, diluted with water and rendered alkaline 
as noted above. The solution is diluted to the same volume 
as that of the solution from the meat and the colors compared. 

The nitrate indicated in the solution of the sample is one- 
fifth of that present, since 20 c.c. out of the 100 c.c. are taken. 
The standard nitrate solution is such that i c.c. contains o.ooi 
gram of potassium nitrate. If the two solutions are of equal 
lint, 0.005 gram of potassium nitrate was in the sample, /. ^., o. 5 
per cent. 

If the two solutions are very different in depth of color, evapo- 
ration of a second portion of standard nitrate solution must be 
made, taking, as far as can be judged, enough, more or less. 



FLESH-FOODS 381 

to approximate closely to the other solution. When the depth 
of color is not widely different in the two solutions, they can be 
compared by pouring out the deeper solution until, when placing 
the glasses side by side upon a pure white surface and looking 
down through the liquids, the tints are sensibly equal. The 
relative volumes of the liquid will then be a basis for calcula- 
tion. For example: 

I gram of sample treated as directed is made up to 50 c.c, 
which volume contains the picrate equivalent of the nitrate 
in 0.2 gram of the sample; if, now, i c.c. of standard nitrate 
also treated and made up to 50 c.c. gives a liquid which is the same 
depth of color as 25 c.c. of the liquid from the sample, then: 

50 c.c. from standard = o.ooi potassium nitrate. 

25 c.c. from sample = o.ooi potassium nitrate. 

50 c.c. from sample = 0.002 potassium nitrate. 

0.002 X 5 = o.oio potassium nitrate = i per cent. 

Injected Meats. — The lower animals are subject to para- 
sitic diseases communicable to human beings. The most 
important are two species of so-called tapeworm and the 
Trichina spiralis. One species of tapeworm, Tcenia saginata, 
is found in one stage of development in beef; another species, 
T. solium, is found in pork. This condition is often termed 
"measles." Trichina spiralis is principally found in pork. 
Many other animal parasites are known, but recognition of 
them belongs to pathology and biology. 

Tcenia saginata Goeze, also called T. mediocannellata, occurs 
in beef as little white cysts among the muscular fibers, like 
knots in wood. The mature animal is developed from the 
cysts when the meat is eaten. It is the common tapeworm 
of the United States. 

Tcenia solium L. occurs in the flesh of the hog. 

Trichina spiralis Owen is a worm that occurs in hog-llcsli 
as light-colored cysts, smaller than a pin's head, and usually 



382 FOOD ANALYSIS 

lying with the long diameter in the direction of the muscular 
fiber. The cysts contain immature worms, which are released 
when the cyst is digested; the worm quickly reaches matur- 
ity, multiplies rapidly, and distributes itself through various 
tissues of the host. 

The detection of the various parasites of meat can often be 
attained by examining with a good hand-glass. With higher 
powers, the organism can be seen in more detail. 

Canned Meats. — These are now usually prepared on a 
very large scale at estabhshments under inspection and hence 
are but little liable to adulteration. Preservatives, except 
common salt and niter, are not likely to be employed. If any 
other preservative should be used it will probably be boric acid 
or possibly salicylic acid, either of which can be easily detected 
in the extract with cold water by methods given elsewhere. 
Tin and sometimes lead are absorbed in small amounts from 
the can or solder. These may be tested for by the methods 
given on page 58. Examination under moderate magnifying 
power will detect parasitic infection. (See pages 378 and 386.) 

Meat-extracts. — These are now offered in great variety. 
Some contain partly digested proteids (proteoses and peptones), 
but in many samples the most abundant nitrogenous ingredients 
are the so-called meat-hases, a class of amido-derivatives of which 
kreatin, kreatinin, and xanthin are examples. Many pro- 
prietary articles, intended especially for invalid feeding, con- 
tain much alcohol and carbohydrates (maltose, lactose, dex- 
trine). Some contain notable amounts of iron and manganese. 

Many investigations of these preparations have been made, 
but the processes of analysis are still in dispute and the results 
obtained by different observers do not agree. The following 
methods are compiled from the work of Allen, Mitchell and 
Grindley. 

Water, Ash, and Total Nitrogen are determined as indicated 
under those titles in the introductory part. 



FLESH-FOODS 383 

Fat is usually present in but small amount, and is extracted 
more accurately by petroleum spirit or carbon tetrachlorid than 
by ether, applying the methods described on pages 41 to 43. 

Insoluble matter, which may include some meat-fiber, is de- 
termined by treating from 5 to 25 grams (depending on whether 
the preparation is solid or liquid) with cold water, filtering, and 
drying the residue at 100°. A microscopic examination of this 
should be made. 

Proteids, Peptones, and Meat-bases, The following method 
has been suggested by Allen, ^^ partly from his own experiments 
and partly from those of Bomer: 

50 c.c. of a solution of a known weight of the sample, of 
such strength as to contain about 1,5 grams of nitrogenous 
bodies, are freed from insoluble material, mixed with i c.c. of 
diluted sulfuric acid (i to 4), and saturated with zinc sulfate 
by stirring in the powdered salt until no more dissolves. Zinc 
sulfate containing the full amount of water of crystallization 
disssolves in about half its weight of water at room tempera- 
ture, but the commercial salt is usually partly effloresced, and 
will often cake when added to the solution. When the liquid 
is saturated with zinc sulfate, the precipitate is assumed to 
contain all the albumin and gelatin and immediate derivatives 
(proteoses), but no peptone. It is separated by filtration, 
washed with a saturated solution of zinc sulfate, and the filter 
and precipitate treated by the Kjeldahl- Gunning method. The 
nitrogen obtained, multiphed by 6.25, will give approximately 
the amount of nitrogenous bodies precipitated. 

The filtrate and washings are made up to 200 c.c, mixed, 
and 100 c.c. transferred to a flask of the larger form described 
on page 33, enough hydrochloric acid added to make the liquid 
strongly acid to litmus, and then bromin water by moderate 
portions, with active shaking or stirring, until there is an 
excess of bromin present. The precipitate may be flocculent 
at first, but most of it soon becomes viscous and adherent. It 



384 FOOD ANALYSIS 

is allowed to stand until the free portions have settled, when 
it is decanted through an asbestos filter either in a Gooch cru- 
cible or in an apparatus similar to that described on page 115. 
The precipitate is washed several times with cold water con- 
taining some hydrochloric acid and bromin, but it is advisable 
to keep the washings at first separate from the main filtrate. 
The contents of the filter-tube are returned to the vessel in 
which the precipitation was made, 10 c.c. of sulfuric acid 
added, and the mass cautiously treated until it chars and vapors 
of bromin are evolved, after which 10 grams of potassium sul- 
fate are added and the operation conducted as described on pages 
33 ^o 37. The nitrogen, multiphed by 6.33, will give ap- 
proximately the peptone. 

The process of A. O. A. C. suggests liquid bromin (2 c.c.) 
instead of bromin water. 

By deducting from the total nitrogen the sum of the nitro- 
gen figures obtained from the zinc sulfate and bromin precipi- 
tates, and multiplying the remainder by 3.12, an approxima- 
tion to the meat-bases will be obtained. These meat-bases 
are in the filtrate from the bromin precipitate, but the bromin, 
hydrochloric acid, and zinc sulfate will be likely to interfere 
with the determination of the nitrogen. The zinc sulfate can 
be removed by cautious addition of either potassium carbon- 
ate or barium hydroxid, but the bromin will be apt to form 
hypobromites, which will decompose some of the meat bases 
with evolution of nitrogen. 

A more satisfactory plan seems to be that outlined by Bau- 
mann and Bomer: The remaining portion, 100 c.c, from the 
zinc sulfate precipitate is mixed with excess of sodium phos- 
phomolybdate (see page 274), by which the meat-bases, pep- 
tones, and ammonium compounds are precipitated. This 
precipitate is removed by filtration under pressure, so as to draw 
out as much as possible of the mother liquor, and the nitrogen 
determined as usual. The nitrogen due to peptone being 



FLESH-FOODS 385 

known, that due to meat-bases and ammonium compounds 
can be calculated. To determine the ammonium compounds, 
a known weight of the original sample should be distilled with 
barium carbonate, the distillate being collected in a knoAvn 
quantity of standard acid, which is afterward titrated. 

Meat-extracts may contain coagulable proteids. These may 
be estimated by rendering the filtrate solution distinctly acid 
with acetic acid and boiling for five minutes. The coagulum 
may be weighed directly or the nitrogen in it estimated by the 
Kjeldahl-Gunning method and multiplied by 6.25 for proteid. 

As solutions of proteids, proteoses, and peptones are strongly 
levorotatory, while most of the meat-bases that occur in these 
extracts are inactive, some information might be gained by con- 
centrating the liquid from the zinc sulfate precipitate and ex- 
amining it in the polarimeter, filtering if necessary. A solution 
that has no appreciable optic activity will not be likely to 
contain much peptone. Another special test that may be ap- 
plied to this liquid is the so-called biuret reaction. Bomer ap- 
plies this as follows: The filtrate from the zinc sulfate pre- 
cipitation is decolorized by shaking with animal charcoal and 
the zinc sulfate decomposed by excess of sodium carbonate or 
cautious addition of barium hydroxid. The filtered solution is 
rendered alkaline with sodium hydroxid and a drop or two of 
very dilute solution of copper sulfate added. Peptones give 
a rose- red tint. 

Preservatives may be added to meat-extracts, although this 
is not usual. Boric acid will be most likely to be used, and 
the methods on page 367 will suffice for its detection. Poi- 
sonous metals arc not Hkcly to be present, but may be sought 
for, if deemed necessary, by the methods given on pages 57 
to 64. Some preparations may require examinations for iron 
and manganese. These will be obtained in solution by heating 
the ash in strong hydrochloric acid, and may be separated and 
determined by the standard methods of mineral analysis. 

34 



o 



86 rOOD ANALYSIS 



Addendum to page 378. — Fresenius & Wackenroder's 
process for the determination of aluminum, as described by 
Chace'^: 

A weighed amount of the finely comminuted sausage is 
heated over a low flame until danger of spurting is past. 
(The low-temperature burner, page 52, figure 31, will be sat- 
isfactory.) The mass is then heated until thoroughly charred, 
cooled and digested for some time on the water-bath with 
hydrochloric acid, filtered, slightly washed, and the filter and 
residue ashed. This ash should be gray and small in amount; 
it is dissolved in hydrochloric acid, the solution filtered and 
the filtrate added to the other solution. Any appreciable 
residue on the filter should be tested for aluminum. The 
combined filtrates are made slightly alkaline by ammonium 
hydroxid, and barium chlorid added until no further precipi- 
tate is formed. This consists of barium phosphate, aluminum 
hydroxid and aluminum phosphate. It is washed, and dis- 
solved in the least possible amount of hydrochloric acid. 
This solution is saturated with barium carbonate. Potassium 
hydroxid is added in excess and the mass digested for some 
time; then sodium carbonate is added, the barium carbonate 
and phosphate separated by filtration and thoroughly washed. 

The filtrate is acidulated with hydrochloric acid, and the 
aluminum determined in the usual wav. 



SPECIFIC GRAVITY OF WATER. 



387 



SPECIFIC GRAVITY OF WATER FROM 0° TO 100' 
Water at 0° = 0.99987 Water at 4° = i. 00000 



I 


0.99992 


26 


0.99686 


51 


0.9S772 


76 


0.97438 


2 


96 


27 


60 


52 


25 


77 


0.97377 


3 


99 


28 


33 


53 


0.98677 


78 


16 


4 


1 .00000 


29 


05 


54 


29 


79 


0.97255 


5 


0.99999 


30 


0.99576 


55 


0.98581 


80 


0.97194 


6 


97 


31 


77 


56 


34 


81 


32 


7 


93 


32 


47 


57 


0.98486 


82 


0.97070 


8 


88 


33 


0.99485 


58 


37 


83 


07 


9 


82 


34 


52 


59 


0.98388 


84 


0.96943 


10 


74 


35 


18 


60 


38 


85 


0.96879 


II 


65 


36 


0.99383 


61 


0.98286 


86 


15 


12 


54 


37 


47 


62 


34 


87 


0.96751 


13 


43 


38 


10 


63 


0.98182 


88 


0.96687 


14 


29 


39 


0.99273 


64 


28 


89 


22 


IS 


16 


40 


35 


65 


0,98074 


90 


0.96556 


16 


00 


41 


0.99197 


66 


19 


91 


0.96490 


17 


0.99884 


42 


58 


67 


0.97964 


92 


23 


18 


65 


43 


18 


68 


08 


93 


0.96356 


19 


46 


44 


0.99078 


' 69 


0.97851 


94 


0.96288 


20 


25 


45 


37 


70 


0.97794 


95 


19 


21 


04 


46 


0.98996 


71 


36 


96 


0.96149 


22 


0.99782 


47 


54 


72 


0.97677 


97 


0.96079 


23 


60 


48 


10 


73 


18 


98 


08 


24 


36 


49 


0.98865 


74 


0-97558 


99 


0.95937 


25 


12 


50 


19 


75 


0.97498 


100 


0.9 5 866 



388 lOOl) ANALYSIS 

Correspondence of Centigrade and Fahrenheit Degrees 



20 



19 
iS 



17 



392.0 
3740 
356.0 



338.0 
16 320.0 
15 302.0 
14 2S4.0 
13 ^ 266.0 
12 248.0 
II 230.0 
10 212.0 
9 1940 

8 176.0 



15S.0 
140.0 



393-8 

375-S 
357-S 
339-8 
321.S 
3038 
2S5.8 
267. S 
249.8 
231-8 
213.S 
195-8 
177.S 
159.8 
141. 8 



5 


1:2.0 


.23.8 


4 


104.0 


105.8 


3 


86.0 


87.8 


2 


68.0 


69.8 


I 


50.0 


51.8 





32.0 


33-8 



395-6 

377-6 
359.6 
341.6 

323-6 
305.6 
287.6 
269.6 
257.6 

233-6 

215.6 

197.6 

179.6 

161. 6 

143-6 

125.6 

107.6 

89.6 

71 6 

53-6 

35-6 



397 


4 


399- 


379 


4 


381. 


361 


4 


363- 


343 


4 


345- 


325 


4 


327- 


307 


4 


309- 


289 


4 


291. 


271 


4 


273- 


253 


4 


255- 


235 


4 


237- 


217 


4 


219. 


199 


4 


201. 


iSi 


4 


183- 


163 


4 


165. 


^45 


4 


M7- 


127 


4 


129. 


109 


4 


III. 


91 


4 


93- 


/J 


4 


75- 


55 


4 


57- 


37 


4 


39- 



15-55° c. 



401.0 


402.8 


404.6 


406.4 


408,2 


383-0 


384-8 


386.6 


3S8.4 


390.2 


3650 


366.8 


368.6 


370.4 


372.2 


347-0 


348.8 


350.6 


352.4 


354-2 


329.0 


330.8 


.S32-6 


334-4 


336.2 


311. 


312.8 


314-6 


316.4 


318.2 


293.0 


294-8 


296.6 


298.4 


303.2 


275.0 


276.8 


278.6 


280.4 


282.2 


257-0 


258.8 


260.6 


262.4 


264.2 


239.0 


240.8 


242.6 


244-4 


246.2 


221.0 


222.8 


224.6 


226.4 


228.2 


203.0 


204.8 


206.6 


208.4 


210.2 


185.0 


186.8 


1S8.6 


190.4 


192.2 


167.0 


168.S 


170.6 


172.4 


174.2 


149.0 


150. S 


152.6 


"54-4 


156.2 


131.0 


132.8 


134-6 


136.4 


138.2 


113. 


114. 8 


116. 6 


118. 4 


120.2 


95-0 


96.8 


98.6 


100.4 


102.2 


77-0 


7S.8 


80.6 


82.4 


84.2 


59.0 


60.8 


62.6 


64.4 


66.2 


41.0 


42.8 


44.6 


46.4 


48.2 


60° F. 
















-I 


-2 


-3 


-4 

24. S 


-5 


-6 


• -7 


-8 


-9 





32.0 


30.2 


28.4 


26.6 


23.0 


21.2 


19.4 


17.6 


15.8 


-I 


14.0 


12.2 


10.4 


8.6 


6.8 


50 


3-2 


1.4 


-0.4 


-2.2 


-2 


-4.0 


-5.8 


-7.6 


-9 4 


-1 1. 2 


-13.0 


-14.S 


-16.6 


-18.4 


-20.2 


-3 


-22.0 


-23.8 


-25.6 


-27-4 


-29.2 


-31.0 


-32.8 


-34.6 


-36.4 


-38.2 



-40° C. = -40° F. 



REFERENCES 



["Bulletin" refers to the publications of the Div. of Chem., U. S. Dept. of Agric] 

' J. A. C. S., 1905, 25. 

2 Bulletin 65. 

^ J. A. C. S., 1905, 141. 

* Advance sheets, Amer. Jour. Pharm. 
^ J. A. C. S., 1903, 1028. 

® Abst. Analyst, 1900, 292. 
^ Unpublished; to appear in Chem. Zeit. 
^ Tollens, Handb. d. Kohlenh., 2, 207. 
^ Abst. Analyst, 1904, 306. 

Z. Anal. C, 1905. 

1 J. A. C. S., 1904, 186. 

^ J. A. C. S., 1904, 1631. 

^ Bulletin 65, also 32d Ann. Rep. Mass. St. B. of H. (1900), 658. 

* Private communication to authors. 
5 J. A. C.S., 1904, 1523- 

« Bulletin 65. 

^ Ding. Polyt. Jour., 253 (1884), 281. 

^ Bulletin 77. 

3 Z. Anal. C, 1877, 145. 
20 Z. Anal. C, 1879, 69. 

2^ Ding. Polyt. Jour., 233 (1879), 229. 

22 Analyst, 1891, 153. 

23 Zeit. Anal. C, 1879, 199. 

2^ Compt. rend., 35 (1851), 573. 
25 J.S.C. I., 1891,233. 
2" Analyst, 1895, 147. 
2' J. A. C.S., 1896,378. 

28 J. A. C. S. 

29 J. C. S. I., 1886, 494- 

30 Zeit. Anal. C, 1877, 145. 

3^ Chem. Anal. Oils, Fats and Waxes, 165. 

32 J. A. C. S., 189s, 935. 

33 J. A. C. S., 1903, 251, 498. 

3^ Chem. Anal. Oils, Fats and Waxes. 

35 J. A. C. S., 1900, 453; 1901, I. 

3" Chem. Anal. Oils, Fats and Waxes, 574. 

3' Much misrepresentation has been made of this matter. Several American 
chemists have ignored our claims to the devising of the process. The 
Gerber method is merely a modification of it. This fact is known to 
chemists of the Department of Agriculture at Washington, yet in the 
"Provisional Methods of Food Analysis," the Gerber method is men- 
tioned as an alternative, as if it were entirely original with Gerber. 

389 



3()0 REFERENCES 

=>« J. A. C. S., 1S99, 503. 

" J. A. C.S., 1904, 1 195. 

*° J. A. C. S., 1904, 1 195. 

*^ Russky Vratch. Abst. Jour. Am. Med. Ass'n., 44 (1905), 1235. 

*^ J. A. C. S., 1900, 207. 

*^ Stokes & Bodmcr suggested 10 minutes' boiling, liut Watts & Tempany 

(Analyst, 1905, 119) show that at least 30 minutes' i)oiling is necessary. 
** Bulletin 65. 
« J. A. C. S., 1905, 270. 

*" Mikroscojjie der Nahrungs- und Genussmillel. 
*^ Food Adulteration and its Detection. 
*^ Bulletin 13. 

*^ Rep. State Board of Health of Ma.ss., 1902, 4S5. 
5" Winton, Bulletin 65. 

^' Rep. State Board of Health of Mass., 190^. 
" J. A. C. S., 1899, 721. 
" Brooks, Rep. Lab. Hvg. N. ]., 190:5. 
^* J. A. C. S. 1899, 257'. 
^^ J. A. C. S., 1902, 1129. 
^^ Food Insj)ection and Analysis, in j)lace. 
" Bulletin 65. 
^^ The reference (Chemist ^ Dnif^f^ist, 57, 732) directs the use of "25 per 

cent, sulfuric acid." It is assumed that proportion by \yeight is meant, 
s^ Rep. State Board of Health of Mass. 
«» J.A. C.S., 1901, 349. 
«i J. A. C.S., 1905,613. 

*^ Leach, Food Inspection and Analysis, 261. 
^^ Bulletin 65. 
«^ Bulletin 64. 
«5 J.A.C.S., 1905, 137. 
«« J.A.C.S., 1905, 138. 
" J.A.C.S., 1903, 16. 
^^ Analyst, 1904, 301. 
88 Edition of 1890. 
" J. A. C. S., 1904, 1627. 
'^ Analyst, 1905, 124. 
" J. A.'C. S., 1900,810. 
'^ Allen's Com'l Org. Anal., i, in place. 
'* Allen's Com'l Org. Anal., i, in place. 
'^ Amer. Chem. J., 1899, 266. 
'® Analyst, 1904, 301. 
" J. A. C. S., 1904, 1086. 
" Bulletin 65. 
'8 Bulletin 65. 
8« Bulletin 65. 
*' Bulletin 65. Some errors in the Bulletin description haye been corrected 

here. 
^^ Com'l Org. Analysis, yol. 4. 
*^ J. A. C. S., 1904, 662; also Fresenius' Quantitatiye Anal., .-\mer. Ed., 1904, 



INDEX 



Abrastol, 77, 86, 220 
Acetyl number, 156 

value, 156 

Acidity, total, 359 
Acid mercuric iodid, 229 
nitrate, 211 



value, 146 

Acorn starch, 90 
. Acrinyl isothiocyanate, 317 
Adams' method, 201 
Agar, 334 
Albumin, 190, 208 
Albuminoid nitrogen, 37 
Alcohol, detection, 352 

determination, 353 

ethyl, 54 

methyl, 54 

detection, 365 



tables, 354-5-6 

Alcoholic beverages, 337 
Ale, 343, 344 
Allihn's method, 117 
Allspice, 311 
Allyl isothiocyanate, 317 
Almen's reagent, 208 
Alum in bread, 102 

— in flour, 97 

Alumina-cream, 118 
Aluminum acetate, 378 

detection, 378 

determination, 386 

Ammonium in baking powders. 
Amphoteric milk, 192 
Annatto, detection, 215, 217 
Antisepticum, 79 
Apparatus, 49 
Arachidic acid, 175 
Arachidin, 174 
Arachis oil, 174 
Arnold's method, 36 
Arrow-root starch, 89, 92 
Arsenic, detection, 60-62, 220 
Asaprol, 86, 87, 220 



109 



Ash, 39 ^ 
Azolitmin, 55 



Babcock's method, 200 
Baking powders, 107 

soda, 105 

Banana starch, 89 
Barley, 97, 100 

starch, 90, 92 

Bases, meat-, 382 
Baudouin's test, 167 
Bean starch, 90, 92 
Bechi's test, 166 
Beef fat, 188 

— stearin, 186 

Beer, 343 

root, 343 

Benzoates, 76, 81 
Benzoic acid, 76, 81 
Birotation, 213 
Bitters in beer, 366 
Biuret reaction, 385 
Bjorkland's test, 180 
Boiled milk, detection, 220 
Boiling-point, 12 

Borax, 78, 82, 239 
Boric acid, 78, 82 
Borofluorids, 78, 82 
Brandy, 341 
Bread, 10 1 

commercial, 102 

Bromas, 277 

Bromin, thermal value, 149 
BruUe's test, 168 
Buckwheat, 97, 100 

starch, 91, 92 

Bumping, prevention, 44, 45 
Burners, 51, 52 

Butter, 230 

cacao-, 179 

colors, 237 

composition, 230 



391 



392 



INDEX 



Butter fat, 189 

milk, 193 

peanut, 174 

vegetable, 179 

Butyrorefractonieter, 154 



Cacao, 273 

butter, 179 

.essence, 277 

husks, 277 

masse, 277 

red, 275 

starch, 90 

Caffearin, 262 
CatTein, 253, 257 

determination, 257 

CafTeol, 262 

Caffetannic acid, 267, 292 
Calculation methods for milk, 204 
Candies, 135 

Cane-sugar, 121 
Canna starch, 89 
Caper tea, 256 
Caramel, 124, 362 
Caryophyllin, 315 
Casein, 190, 208 
Cassia, 313 

oil, 314 

Catsup, S33 
Centrifuge, 50, 203 
Cereals, 95 

starches, 91 

Champagne, 346 
Cheese, 240 
Chemicals, 49 
Chicory, 266 
Ching suey, 256 
Chocolate, 273 

nuts, 276 

Cholesterol, 160 
Chromium, detection, 58 
Cider, 337 

vinegar, 284 

Cinnamon, 312 

oil, 314 

starch, 91 

Citric acid, determination, in milk. 

Clove oil, 315 
Cloves, 315 

Cobalt nitrate test, no 
Cochineal, 56, 72 
Cochran's method, 224 
Cocoa, 277 



Cocoas, soluble, 277 
Coconut oil, 178 

olcin, 179 

stearin, 179 

Coffee, 262 

essence, 272 

extracts, 272 

Colors, 64-75 

in butter, 237 

in candies, 136 

in meat, 377 

in milk, 215 

in wine, 361 

test for oils, 137 

Colostrum, 195 

Colza oil, 178 
Condensed milk, 222 
Condensers, 45-8 
Condiments, 282 
Confections, 135 
Congou paste, 256 

tea, 256 

Constants for oils, 164, 165 
Copper, detection, 59 

hydro xid mixture, 37 

in bread, 104 

in flour, 98, 104 

Coriander seed, 301 
Corn, Dhoura, 301 

meal, 97, 100 

oil, 172 

starch, 91, 92 

Cottonseed oil, 171 

stearin, 172 

Cream, 193 

evaporated, 222 

of tartar, 105 

Cribb's condenser, 45 
Crude fiber, 38 
Cryoscoi)y of milk, 214 
Cumarin, 324 



Dalican's titer test, 1 1 
Desserts, 335 
Dextrin in honey, 131 

in %\-inc, 359 

Dextrose, determination, 113 
Dhoura corn, 301 

starch, 90 

Distillation, 44 
Doughing test, 96 
Dr}ing of oils, 154 

ovens, 28, 30 



INDEX 



393 



Drying property, 154 
Dry wine, 346 



Egg colors, 72 

detection, 335 

Elaidin test, 152 

Electrolytic methods, 116 

Ergot, 98 

Erucin, 178 

Essence of cacao, 277 

— of coffee, 292 

Ether purification, 54 
Eugenic acid, 315 
Eugenol, 315 
Evaporated cream, 222 
Extract, 27 
Extraction apparatus, 41 



-Facing coffee, 264 

tea, 258 

Fat of milk, 190, 200 
Fats,_ 137 

Fehling's solution, 113 
Fermented milk, 248 
Fiber, crude, 38 
Filter-tubes, 114, 115 
Fixed solids, 27 
Flesh-foods, 373 
Flour, 93, 97 
Fluorescence, 23 
Fluorids, 78, 82 
Foreign leaves in tea, 260 
Formaldehyde, 77, 8^, 218 
Formalin, 77 
Fractional distillation, 49 
Furfural test, 167 
Fusel oil, determination, 363 



GaLACTOSAZONE, III 

Gallisin, 125 
Gelatin, detection, 217 
Gin, 341 
Ginger, 306 

starch, 89 

Gingli oil, 177 
Gliadin, 95 
Globulin, 95 
Glucosazone, 1 1 1 
Glucose, 125 
Glutenin, 95 
Gluten test, 96 
Glycerol in wine, 350 



Glycerol soda, 143 
Glycogen, 375 
Graham flour, 97 
Grape-juice vinegar, 283 
Grape-sugar, 125 
Gmn in wine, 359 
Gutzeit's test, 61 
Gypsum in bread, 104 



Hager's test, 352 
Halphen's test, 166 
Hanus' reagent, 140 
Hehner value, 155 
Honey, 130 

Horseflesh, detection, 375 
Hiibl's reagent, 139 
Hydrometers, 6 
Hydronaphthol, 77 



Ice-cream, 335 
Immiscible solvents, 43, 55 
Improvers, ineat, 378 
Index of refraction, 153 
Indicators, 55 
Indigo, detection, 258 
Insoluble acids, 155 
Inversion methods, 119, 227 
Inverted condenser, 48 
Invert-sugar, 119, 227 
lodin number, 139 

value, 139 

Iron, detection, 58 



Jams, 327 
Jellies, 327 

Kefyr, 249 

Kjeldahl- Arnold method, 36 

Gunning method, 32 

Kottstorfer number, 145 
Kumiss, 248 



LaCTOSAZONE, III 

Lactose, no, in, 191, 210 

Lager beer, 343, 344 

Lard, 180 

Laurent polarimctcr, 13 

Laureol, 179 

Laurin, 178 

Lead, detection, 58 

subacetatc, 118 



;94 



INDEX 



Leavening materials, 105 
LetTmann-Bcam method, 203 
Leguminous Hours, 99 
Lemon extract, 324 

juice, 330 

sirup, 330 

Lentil starch, 90 
Lieben's test, 352 
Lie tea, 256 
Lignoceric acid, 175 
Litmus, 55 
Livache's test, 154 
Long pepper, 301 
Low wine, 283 



Mace, 308 

false, 309 

Maize, 97, 100, 104 
oil, 172 

starch, 91, 92 

Malic acid, 290 

value, 129 

Malt extract, 93, 371 

liquors, 342 

vinegar, 285 

Maltosazone, 1 1 1 
Maple sugar, 127 

sirup, 127 

Maranta starch, 89 
Marsh's test, 62 
Maumene's test, 14S 
Mead, 343 

Meal, 93 

Meat bases, 382 

— extracts, 382 

Meats, 373 
Melting-point, 7 
Mercuric iodid, acid, 229 

nitrate, acid, 2 1 1 

Metals, poisonous, 57 
Methyl alcohol, 54 

detection, 365 

orange, 56 

Microscope, 23 
Milk, 190 

ash, 191, 200 

boiled, 193, 220 

condensed, 222 

enzyms, 191 

serum, 193 

sugar, 191 



Miscible solvents, 41 
Mixed llours, 99 
Mohr's centimeters, 20 



Molasses, 123 
Mother cloves, 315 

starch, 89 

Must, 348 
Mustard, 317 

oil, 317 

Myristic acid, 308 
Myristicol, 308 
Myronic acid, 317 
Myrosin, 317 



Naphthol, 77, 85 
Nickel, detection, 58 
Nitrogen, albuminoid, 37 

total, 32 

Normal weight, 20 
Nucoline, 179 
Nutmeg, 307 

starch, 90 

oil, 307 

Nutshells, 300 



Oats, 97, 99 
Oat starch, 91, 92 
Oil, arachis, 174 

cassia, 314 

cinnamon, 314 

cloves, 315 

coconut, 178 

colza, 178 

corn, 172 

^ — cottonseed, 171 

gingli, 177 

maize, 172 

mustard, 317 

nutmeg, 307 

olive, 168 

peanut, 174 

pepper, 293 

rape, 178 

sesame, 177 

teel, 177 

Oleomargarin, 232 
Oleorefractometer, 153 
Olive oil, 168 

stones, 298 

Original solids, 287 
Ovens, 28, 30 



Paraffin in oleomargarin, 240 
Peanut butter, 174 
oil, 174 



INDEX 



395 



Pea starch, 90 
Penumbral polarimeters, 13 
Pepper, 293 

— cayenne^ 304 

■ long, 302 

starch, 91 

Pepperette, 298 
Peptones, determination, 383 
Perry, 337 
Petroleum spirit, 55 
Phenol, 85 
Phenolphthalein, 56 
Phenylhydrazin test, in 
Phvtosterol, 161 
Pintus, A. S., 86 
Piperidin, 293 
Piperin, 293 
Plastering of wine, 350 
Platinum, care of, 53 
Poisonous metals, 57 
Poivrette, 298 
Polarimetry, 13 
Porter, 344 
Potato flour, 99 

starch, 89, 91, 92 

Preservaline, 78 
Preservatives, 76, 378 
Process butter, 236 
Proteids, determination, 205 
Proteoses, determination, 383 
Prune juice, detection, 362 
Prussian blue, detection, 258 
Putrefaction, detection, 378 
Pyknometer, 2 



QuERCiTANNic acid, 312 



Rape oil, 178 
Reagents, 25, 52 
Recknagel's phenomenon, 192 
Refraction index, 153 
Refractometer, 153 
Reichert-Meissl number, 143 
Reichert number, 143 
Reinsch's test, 60 
Renovated butter, 236 
Rex magnus, 78 
Rice starch, 91, 92 
Ritthausen method, 207 
Root beer, 343 
Rum, 341 
Rye flour, 96, 99 
starch, 90, 92 



Saccharin, 77, 80, 361 

Sago starch, 90 

Salicylic acid, 76, 80, 362 

Salol', 85 

Saponification equivalent, 146 

— - value, 145 

Sausage, adulteration of, 378 

Sawdust in flour, 100 

Scales for polarimeter, 20 

Scheibler's method, 21 

Schmidt and Hansch polarimeter, 15 

scale, 20 

Separated milk, 193 
Sesame oil, 177 
Silicofluorids, 78, 82 
Sirup, 123 
Sitosterol, 161 
Sodium benzoate, 76 

phosphomolybdatc, 274 

Solidifying-points, 7 
Solids, original, 287 
Soluble acids, 155 

cocoas, 277 

Solvents, immiscible, 43, 55 

miscible, 41 

Soxhlet's method, 210 
Specific gravity, i 

bottle, 2 

rotatory power, 19 

temperature reaction, 148 



Spectroscope, 21 

Spices, 291 

Spirits, 338 

Sprengel tube, 3 

Standard acid, 56 

Stannous chlorid in bread, 105 

in sugar, 122 

Starch, 87 

detection, 87 

determination, 93 

indicator, 56 

Starches, characters of, 89, 90, 91 
Stearin, beef, 186 

coconut, 179 

cottonseed, 172 

Stout, 343 

Stutzer's method, 37, 246 

Sublimation, 44, 49 

Sucrose, 121 

Sugar, cane-, no 

Sugars, no 

Sugar scale, 20 

Sulfites, 78, 359 

Sulfur chloricl test, 186 

Sulfuric acid in vinegar, 2S9 



396 



INDEX 



Sulfurous acid determination, 360 
Szoiiibathy's lube, 45 

Table accessories, ^^;^ 

Tajnia, forms of, 381 

Tallow, 187 

Tannin, determination, 292 

Tapeworm, 381 

Tapioca starch, 90 

Tartaric acid, ^;^2 

Tea, 252 

Teel oil, 177 

Terra alba in bread, 104 

Thein, 253 

Theobromin, 273 

Thermal reactions, 148-150 

Tin, detection, 58, 59 

in bread, 105 

Titer-test in sugar, 122 
Tocher's test, 168 
Treacle, 123 
Trichina, 38 1 
Turmeric, 310 
starch, 89 

Ultramarine blue, 122 
Unsaponifiable matter, 159 



Vanilla extract, 320 
Vanillin, ^2^^ 
Vegetable butter, 179 
Vegetaline, 179 
Vinegar, 282 

cider, 284 

malt, 285 

spirit, 285 

wine, 283, 284 

Viscosity, 158 
Volatile acids, 142 

Water determination, 27 

specific gravity of, 386 

Weissbier, 343 
Werner-Schmid method, 202 
Weston distillation apparatus, 45 
Westphal balance, 4 
Wheat, 96, 99 

starch, 90 

Whey, 193 
Whiskey, 339 
Wild's scale, 21 
Wine, 345 

low, 283 

vinegar, 283 

Wool test, 64 



Valexta's test, 147 



Zrxc, detection, 58, 59 



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